Category: Meeting Updates

Elacestrant in Metastatic Breast Cancer Progressing on CDK4/6 Therapy and ESR1-Mutant Subtype

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SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. Approximately 290,560 new cases of breast cancer will be diagnosed in 2022 and about 43,780 individuals will die of the disease, largely due to metastatic recurrence. Approximately 70% of breast tumors express Estrogen Receptors and/or Progesterone Receptors. The most common subtype of metastatic breast cancer is Hormone Receptor-positive (HR-positive), HER2-negative breast cancer (65% of all metastatic breast tumors), and these patients are often treated with anti-estrogen therapy as first line treatment. However, resistance to hormonal therapy occurs in a majority of the patients, with a median Overall Survival (OS) of 36 months. With the development of Cyclin Dependent Kinases (CDK) 4/6 inhibitors, endocrine therapy plus a CDK4/6 inhibitor is the mainstay for the management of ER+/HER2- metastatic breast cancer as first-line therapy. Even with this therapeutic combination, most patients will eventually experience disease progression, including development of ESR1 (Estrogen Receptor gene alpha) mutations.

ESR1 is the most common acquired mutation noted in breast tumors as they progress from primary to metastatic setting. These mutations promote ligand independent Estrogen Receptor activation and have been shown to promote resistance to estrogen deprivation therapy. It appears that ESR1 mutations are harbored in metastatic ER+ breast cancers with prior Aromatase Inhibitor (AI) therapy, but not in primary breast cancers, suggesting that ESR1 mutations may be selected by prior therapy with an AI, in advanced breast cancer. In a recently published study (JAMA Oncol.2016;2:1310-1315), ESR1 mutations Y537S and D538G mutations detected in baseline plasma samples from ER+/HER- advanced breast cancer patients, was associated with shorter Overall Survival. In this study it was noted that there was a three-fold increase in the prevalence of these mutations in patients who had failed first line hormonal therapy for metastatic disease, compared with those who were initiating first line therapy for advanced breast cancer (33% versus 11%).

Fulvestrant is a parenteral, Selective Estrogen Receptor Degrader (SERD) and is the only SERD approved for the treatment of postmenopausal women with HR-positive metastatic breast cancer. However, acquired ESR1 mutations can also occur following Fulvestrant treatment, possibly because of poor bioavailability and incomplete ER blockade when administered intramuscularly. There is therefore an urgent unmet need for an alternate SERD that has activity in tumors harboring ESR1 mutations, and has improved bioavailability allowing oral administration.

Elacestrant is an oral, nonsteroidal, Selective Estrogen Receptor Degrader (SERD) that degrades the Estrogen Receptor (ER) in a dose-dependent manner and inhibits estradiol-dependent functions of ER target gene transcription induction and breast cancer cell proliferation. Estradiol-stimulated tumor growth was diminished by Elacestrant in the ER+ xenograft models derived from heavily pretreated patients, including models resistant to CDK 4/6 inhibitors, Fulvestrant and those harboring ESR1 mutations Y537S and D538G. In an early Phase I trial, Elacestrant was noted to have an acceptable safety profile, and demonstrated single-agent activity with confirmed Partial Responses in heavily pretreated patients with ER+ metastatic breast cancer.

EMERALD trial is a multicenter, International, randomized, open-label, Phase III study designed to evaluate the benefit of Elacestrant in patients with ER+ HER2- advanced or metastatic breast cancer. In this study, 477 postmenopausal women with ER+/HER2- metastatic breast cancer were randomly assigned 1:1 to receive either Elacestrant 400 mg orally daily (N=239) or the Standard of Care which included investigator’s choice of Fulvestrant or an Aromatase Inhibitor including Anastrozole, Letrozole, or Exemestane (N=238). Treatment was given until disease progression. Both treatment groups were well balanced. The median patient age was 63 years, and patients must have progressed or relapsed on or after 1 or 2 lines of endocrine therapy for advanced disease, one of which was given in combination with a CDK4/6 inhibitor, had 1 or fewer lines of chemotherapy for advanced disease, and had an ECOG performance status of 0 or 1. In the study, 48% had tumors with mutated ESR1 and these patients were evenly distributed in both treatment groups. Patients were stratified by ESR1-mutation status, prior treatment with Fulvestrant, and visceral metastases. The co-Primary end points were Progression Free Survival (PFS) in the overall population, and in those with ESR1 mutations. Overall Survival (OS) was a Secondary end point.

Treatment with Elacestrant resulted in a statistically significant and clinically meaningful improvement in PFS, compared with Standard of Care. There was a 31% reduction in the risk of progression or death in the Elacestrant group for all patients (HR=0.69; P=0.0018) and a 45% reduction in the risk of progression or death among those with ESR1 mutations (HR=0.55; P=0.0005).

The PFS at 12 months with Elacestrant was 22.3% in all patients compared with 9.4% for those receiving the Standard of Care treatment. Among the ESR1 mutation group, the 12 month PFS rate was more pronounced and was 26.8% with Elacestrant, compared to 8.2% with Standard of Care. The benefits with Elacestrant compared with Standard of Care, was consistent across multiple prespecified subgroups including patients who had received prior Fulvestrant. There also was a trend toward improved Overall Survival in patients who received Elacestrant, compared with Standard of Care. The final OS results however are not expected until late 2022. Elacestrant was well tolerated and treatment discontinuation rate was not significantly different between the two treatment groups.

It was concluded that Elacestrant is the first oral Selective Estrogen Receptor Degrader that demonstrated significant and clinically meaningful improvement in PFS compared with Standard of Care endocrine therapy in patients with ER+/ HER2- metastatic breast cancer in the second/third line after treatment with a CDK4/6 inhibitor, and has the potential to become the new standard of care in the study population.

Elacestrant, an oral selective estrogen receptor degrader (SERD), vs investigator’s choice of endocrine monotherapy for ER+/HER2- advanced/metastatic breast cancer (mBC) following progression on prior endocrine and CDK4/6 inhibitor therapy: Results of the EMERALD phase 3 trial. Bardia A, Neven P, Streich G, et al. Presented at 2021 San Antonio Breast Cancer Symposium; December 7-10, 2021; San Antonio, TX. Abstract GS2-02.

Defining Patient Groups With Triple Negative Breast Cancer Who Derive Benefit From KEYTRUDA® plus Chemotherapy

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SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. Approximately 284,200 new cases of breast cancer will be diagnosed in 2021 and about 44,130 individuals will die of the disease, largely due to metastatic recurrence. Triple Negative Breast Cancer (TNBC) is a heterogeneous, molecularly diverse group of breast cancers and are ER (Estrogen Receptor), PR (Progesterone Receptor) and HER2 (Human Epidermal Growth Factor Receptor-2) negative. TNBC accounts for 15-20% of invasive breast cancers, with a higher incidence noted in young patients. It is usually aggressive, and tumors tend to be high grade and patients with TNBC are at a higher risk of both local and distant recurrence. Those with metastatic disease have one of the worst prognoses of all cancers with a median Overall Survival of 13 months. The majority of patients with TNBC who develop metastatic disease do so within the first 3 years after diagnosis, whereas those without recurrence during this period of time have survival rates similar to those with ER-positive breast cancers.

The lack of known recurrent oncogenic drivers in patients with metastatic TNBC, presents a major therapeutic challenge. It appears that there are subsets of patients with TNBC who may be inherently insensitive to cytotoxic chemotherapy. Three treatment approaches appear to be promising and they include immune therapies, PARP inhibition, and inhibition of PI3K pathway. Previously published studies have shown that presence of tumor-infiltrating lymphocytes was associated with clinical benefit, when treated with chemotherapy and immunotherapy, in patients with TNBC, and improved clinical benefit was observed in patients with immune-enriched molecular subtypes of metastatic TNBC.

KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2. It thereby reverses the PD-1 pathway-mediated inhibition of the immune response, and unleashes the tumor-specific effector T cells. The rationale for combining chemotherapy with immunotherapy is that cytotoxic chemotherapy releases tumor-specific antigens, and immune checkpoint inhibitors such as KEYTRUDA® when given along with chemotherapy can enhance endogenous anticancer immunity. Single agent KEYTRUDA® in metastatic TNBC demonstrated durable antitumor activity in several studies, with Objective Response Rates (ORRs) ranging from 10-21% and improved clinical responses in patients with higher PD-L1 expression. When given along with chemotherapy as a neoadjuvant treatment for patients with high-risk, early-stage TNBC, KEYTRUDA® combination achieved Pathological Complete Response rate of 65%, regardless of PD-L1 expression. Based on this data, KEYTRUDA® in combination with chemotherapy was studied, for first line treatment of advanced TNBC.

KEYNOTE-355 is a randomized, double-blind, Phase III study, which evaluated the benefit of KEYTRUDA® in combination with one of the three different chemotherapy regimens, nab-Paclitaxel, Paclitaxel, or the non-taxane containing Gemzar/Carboplatin, versus placebo plus one of the three chemotherapy regimens, in patients with previously untreated or locally recurrent inoperable metastatic TNBC. In this study, 847 patients were randomized 2:1 to receive either KEYTRUDA® 200 mg IV on day 1 of each 21-day cycle along with either nab-Paclitaxel 100 mg/m2 IV on days 1, 8 and 15 of each 28-day cycle, Paclitaxel 90 mg/m2 IV on days 1, 8 and 15 of each 28-day cycle, or Gemcitabine 1000 mg/m2 IV plus Carboplatin AUC 2, IV on days 1 and 8 of each 21-day cycle (N= 566) or placebo along with one of the three chemotherapy regimens (N= 281). This study was not designed to compare the efficacy of the different chemotherapy regimens. Treatment was continued until disease progression. Patients were stratified by chemotherapy, PD-L1 tumor expression (CPS-Combined Positive Score of 1 or higher versus CPS of less than 1), and prior treatment with the same class of neoadjuvant/adjuvant chemotherapy (Yes versus No). The baseline characteristics of treatment groups were well-balanced. The co-Primary end points of the trial were Progression Free Survival (PFS) and Overall Survival (OS) in patients with PD-L1-positive tumors, and in all patients. Secondary end points were Objective Response Rate (ORR), Duration of Response, Disease Control Rate, and Safety.

In the primary analysis of the KEYNOTE-355 trial, the Overall Survival results after a median follow up of 44.1 months in the subgroup of patients with PD-L1 CPS (Combined Positive Score) of 10 or more was significantly better with first line KEYTRUDA® plus chemotherapy versus placebo plus chemotherapy (23.0 months versus 16.1 months, respectively; HR=0.73; P=0.0093). This represented a 27% reduction in the risk of death with the KEYTRUDA® combination. KEYTRUDA® in combination with chemotherapy, also significantly improved PFS in patients with CPS (Combined Positive Score) of 10 or greater. The median PFS was 9.7 months for KEYTRUDA® plus chemotherapy, compared with 5.6 months for placebo plus chemotherapy (HR=0.65, P=0.0012). This represented a 35% reduction in the risk of disease progression. However, among patients with CPS of 1 or greater, the median PFS was not considered statistically significant, based on prespecified statistical criteria.

The researchers here in presented the results of a subgroup analysis, stratified by levels of PD-L1 expression, as assessed by CPS score. In the subgroups with CPS scores of less than 1 and 1-9, Overall Survival was similar for KEYTRUDA® plus chemotherapy and placebo plus chemotherapy. However, in subgroups with CPS 10-19 and CPS 20 or more, there was sustained separation of the Overall survival curves starting at approximately 10 months and the survival was improved by about 28%.

The authors noted that the general trend for PFS was consistent with that observed for Overall Survival, with improving PFS trend among those subgroups with PD-L1 enriched CPS of 10 or more. In the subgroup of patients with a CPS of 10-19 and CPS of 20 or more, the addition of KEYTRUDA® to chemotherapy resulted in a more sustained separation of PFS curves, beginning at approximately 4 months, compared with placebo plus chemotherapy. The Hazard Ratios for these two groups were 0.70 and 0.62, respectively. Toxicities of any grade were reported in 96% of the experimental group and 95% of the placebo plus chemotherapy group. The rate of Grades 3-5 treatment-related adverse events was 68.1% and 66.9%, respectively and the majority of treatment discontinuations in this study were for progressive disease.

The researchers based on this subgroup analyses concluded that a CPS of 10 or more is a reasonable cutoff to define the population of women with metastatic Triple Negative Breast Cancer, expected to derive treatment benefit from KEYTRUDA® plus chemotherapy, lending further support to KEYTRUDA® plus chemotherapy as a standard of care treatment regimen for this group of patients.

Final results of KEYNOTE-355: randomized, double-blind, phase 3 study of pembrolizumab + chemotherapy vs placebo + chemotherapy for previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer. Cortés J, Cescon DW, Rugo HS, et al. Presented at: 2021 San Antonio Breast Cancer Symposium; December 7-10, 2021; San Antonio, TX. Abstract GS1-02.

Elevated White Cell Count and Risk of Thrombotic Events in Polycythemia Vera

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SUMMARY: Polycythemia Vera (P. Vera) is a clonal myeloproliferative neoplasm characterized by isolated erythrocytosis in a majority of the patients, with the remaining demonstrating leukocytosis and/or thrombocytosis along with erythrocytosis. Patients usually present with this disorder in their sixth decade and are often asymptomatic, with the diagnosis made incidentally on routine laboratory evaluation. About 30% of the patients however, may initially present with a thrombotic episode, whereas a small percentage of patients may present with disease related symptoms such as pruritus and fatigue. The conventional risk factors for thrombotic events in MyeloProliferative Neoplasms (MPN) are age more than 60 years and prior thrombosis, and the presence of both these risk factors is associated with a 7-fold increased risk of thrombosis.

Overactivation of the JAK-STAT signal transduction pathway caused by V617F mutation has been implicated in majority of the patients with P. Vera. This pathway normally is responsible for passing information from outside the cell through the cell membrane to the DNA in the nucleus for gene transcription. Janus Kinase (JAK) family of tyrosine kinases are cytoplasmic proteins and include JAK1, JAK2, JAK3 and TYK2. JAK1 helps propagate the signaling of inflammatory cytokines whereas JAK2 is essential for growth and differentiation of hematopoietic stem cells. These tyrosine kinases mediate cell signaling by recruiting STAT’s (Signal Transducer and Activator of Transcription), with resulting modulation of gene expression. In patients with P. Vera, the aberrant myeloproliferation is the result of dysregulated JAK2-STAT signaling as well as excess production of inflammatory cytokines, associated with this abnormal signaling. JAK2 mutations such as JAK2 V617F are seen in approximately 95% of patients with P. Vera.Molecular-Mechanisms-of-MPNs

Studies have shown that JAK2 mutations that result in the overproduction of erythrocytes, leukocytes, and platelets in P. Vera also promote direct activation of leukocytes and platelets. Activated platelets and leukocytes bind to each other and activate endothelial cells, which may in turn contribute to the prothrombotic state. The prospective CYTO-PV trial published in 2011, established that maintaining hematocrit less than 45% through phlebotomies and/or cytoreductive drugs significantly decreased the risk of thrombotic events in P. Vera patients. Even though several retrospective analyses strongly suggest an association between leukocytosis and thrombosis, leukocytosis particularly at the time of the thrombotic event in P. Vera patients, no prospective trial has been conducted to assess the impact of WBC counts on thrombotic risk in P. Vera.

The REVEAL study is a large, real-world, multicenter, prospective, noninterventional, observational study, in which patients with P. Vera from US community practice and academic centers were enrolled , to evaluate the association between elevated blood counts and occurrence of thrombotic events in patients with P. Vera, using data from the REVEAL study.

This study analyzed the data of 2271 eligible patients for this analysis (78% high risk and 22% low risk). The median patient age was 66 years and 54% were male. The median disease duration was 4.1 years, 20% had a history of thrombotic events and majority of patients (53%) were receiving Hydroxyurea. Patient data was collected at diagnosis, at a 6-month period, and during follow up, 3 years from last patient enrollment, between July 2014 and August 2019 and the researchers analyzed the association between blood counts and thrombotic events. Out of 106 patients who had thrombotic events, 30 had arterial thrombotic events, most commonly, Transient Ischemic Attack and 76 had venous thrombotic events, most commonly, Deep Vein Thrombosis.

It was noted that hematocrit greater than 45% versus 45% or less (P=0.0028), WBC more than 11×109/L versus 11×109/L or less (P<0.0001), and Platelet counts more than 400×109/L versus 400×109/L or less (P=0.0170) were each associated with increased risk of thrombotic events. A WBC count of 11×109/L or more was associated with the highest thrombotic event risk compared with WBC count less than 7×109/L (P<0.0001). In all models analyzed, advanced age and history of thrombotic events, were associated with increased thrombotic event risk.

The authors concluded that in this analysis of the largest real-world cohort of P. Vera patients to date, hematocrit more than 45%, as well as WBC more than 11×109/L and Platelet counts more than 400×109/L, were each associated with increased risk of thrombotic events. The authors added that these data support the incorporation of blood count values into risk stratification and treatment strategies for patients with P. Vera in clinical practice, and to move beyond the conventional risk model.

A Real-World Evaluation of the Association between Elevated Blood Counts and Thrombotic Events in Polycythemia Vera (Analysis of Data from the REVEAL Study). Gerds AT, Mesa RA, Burke JM, et al. Presented at: 2021 ASH Annual Meeting and Exposition; December 11-14, 2021; Atlanta, GA. Abstract 239.

Long Term Survival Benefit with Maintenance ONUREG® in AML Patients

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SUMMARY: The American Cancer Society has estimated that in 2021, 20,240 new cases of Acute Myeloid Leukemia (AML) were diagnosed in the United States and 11,400 patients died of the disease. AML is one of the most common types of leukemia in adults and can be considered as a group of molecularly heterogeneous diseases with different clinical behavior and outcomes. A significant percentage of patients with newly diagnosed AML are not candidates for intensive chemotherapy or have disease that is refractory to standard chemotherapy. Even with the best available therapies, the 5 year Overall Survival (OS) in patients 65 years of age or older is less than 5%. Cytogenetic analysis has been part of routine evaluation when caring for patients with AML. By predicting resistance to therapy, tumor cytogenetics will stratify patients based on risk, and help manage them accordingly. Even though cytotoxic chemotherapy may lead to long term remission and cure in a minority of patients with favorable cytogenetics, patients with high risk features such as unfavorable cytogenetics, molecular abnormalities, prior myelodysplasia and advanced age, have poor outcomes with conventional chemotherapy alone. More importantly, with the understanding of molecular pathology of AML, personalized and targeted therapies are becoming an important part of the AML treatment armamentarium.

Cytotoxic chemotherapy for AML often consists of induction therapy to achieve remission, followed by consolidation therapy. However, standard induction chemotherapy achieves Complete Remission in only 40-60% of AML patients older than 60 years of age, and majority of these patients will eventually relapse. This had been attributed to clonal evolution and epigenetic reprogramming, leading to aberrant DNA methylation, and persistence of leukemia-initiating cells.

Longer duration of first remission is associated with better survival outcomes. Postremission maintenance therapies to prevent early AML relapse has been an area of active research with little progress made until now. Patients with AML who are under age 55 with high-risk cytogenetics, in first clinical remission,are considered for allogeneic Hematopoietic Stem Cell Transplantation (HSCT), as this has shown to offer survival advantage over conventional chemotherapy. This therapeutic option however is not feasible for many elderly patients.

Oral Azacitidine (ONUREG®) is a hypomethylating agent that has a distinct pharmacokinetic as well as pharmacodynamic profile from the parenteral Azacitidine preparation, and can be administered in extended dosing schedules (for 14-21 days per 28-day treatment cycle) to sustain therapeutic activity.

ONUREG® is the first and only FDA-approved therapy indicated for continued treatment of adult patients with AML who achieved first Complete Remission (CR) or Complete Remission with incomplete blood count recovery (CRi) following intensive induction chemotherapy, and are not able to complete intensive curative therapy.

This FDA approval was based on an International, double-blind, placebo-controlled, Phase III QUAZAR AML-001 trial, in which ONUREG® was evaluated as maintenance therapy in patients with AML, who were in first remission after intensive chemotherapy. Eligible patients were 55 years of age or older, were in complete remission with or without complete blood count recovery, and were not candidates for Hematopoietic Stem Cell Transplantation. Patients (N=472) were randomly assigned to receive ONUREG® 300 mg orally (N=238) or placebo (N=234), once daily for 14 days of a 28-day cycle. The median age was 68 years. The Primary end point was Overall Survival (OS). Secondary end points included Relapse Free Survival (RFS) and Health-Related Quality of Life.

At the time of the primary analysis in 2019, with a median follow up of 41.2 months, maintenance treatment with ONUREG® significantly prolonged median OS, when compared to placebo (24.7 months versus 14.8 months; P<0.001). The median RFS was also significantly longer with ONUREG® than with placebo (10.2 months versus 4.8 months; P<0.001). These survival benefits were demonstrated in most treatment subgroups. Further, with a median follow up of 51.7 months, the median OS remained unchanged, and the median OS with oral ONUREG® was 24.7 months versus 14.8 months with placebo (HR=0.69; P=0.0008). The 3-year OS rates in the experimental and control arms were 37.4% and 27.9%, respectively and at 5 years were 26.2% and 19.2%, respectively. Overall Quality of life was preserved while on treatment with ONUREG®. The most common adverse reactions associated with ONUREG® treatment were nausea, vomiting, diarrhea, abdominal pain, constipation, fatigue/asthenia, febrile neutropenia and pneumonia.

The authors concluded that maintenance treatment with ONUREG® was associated with significantly longer Overall and Relapse Free Survival when compared to placebo, among elderly patients with AML, who were in remission after chemotherapy. This survival benefit was maintained with one additional year of follow up. The researchers added that these updated data suggests that maintenance therapy with ONUREG® provides a sustained, long term Overall Survival benefit in elderly patients with AML in first remission.

Long-Term Overall Survival (OS) with Oral Azacitidine (Oral-AZA) in Patients with Acute Myeloid Leukemia (AML) in First Remission after Intensive Chemotherapy (IC): Updated Results from the Phase 3 QUAZAR AML-001 Trial. Wei AH, Döhner H, Sayar H, et al. Blood. 2021;138(suppl 1):871. doi:10.1182/blood-2021-147501.

Postmenopausal Women with Node Positive Breast Cancer May Not Benefit From Chemotherapy

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SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. Approximately 284,200 new cases of breast cancer will be diagnosed in 2021 and about 44,130 individuals will die of the disease, largely due to metastatic recurrence. Approximately 25% of patients with Hormone Receptor (HR)-positive, HER2-negative early breast cancer have metastatic lymph node involvement and two third of these patients are postmenopausal. Majority of these patients currently receive adjuvant chemotherapy.

The Oncotype DX breast cancer assay, is a multigene genomic test that analyzes the activity of a group of 21 genes and is able to predict the risk of breast cancer recurrence and likelihood of benefit from systemic chemotherapy, following surgery, in women with early stage breast cancer. Chemotherapy recommendations for early stage, HR-positive, HER-negative, early stage breast cancer patients, are often made based on tumor size, grade, ImmunoHistoChemical (IHC) markers such as Ki-67, nodal status and Oncotype DX Recurrence Score (RS) assay.

In the ground-breaking TAILORx (Trial Assigning Individualized Options for Treatment) study which enrolled 10,273 patients with HR-positive, HER2-negative, axillary node-negative breast cancer, patients were divided into three groups based on their Recurrence Score. Patient with Intermediate Recurrence Score of 11-25 were randomly assigned to receive endocrine therapy alone or endocrine therapy and adjuvant chemotherapy. There was no benefit noted from adding chemotherapy to endocrine therapy, for women older than 50 years in this Intermediate RS group, suggesting that a significant percentage of women with node-negative breast cancer do not achieve substantial benefit from chemotherapy. For women 50 years old or younger who received chemotherapy and had a Recurrence Score of at least 16, there was a lower rate of distant recurrence, and the absolute benefit increased with increasing recurrence score. Further, the risk of recurrence and benefit of chemotherapy was further influenced by the tumor size and grade.

Whether the results of TAILORx can be extrapolated to women with node-positive breast cancer has remained unclear. It is estimated that approximately 85% of women with node-positive disease have Recurrence Score results of 0-25. The RxPONDER (A Clinical Trial RX for Positive Node, Endocrine Responsive Breast Cancer) trial was designed to determine the benefit of chemotherapy, in patients with HR-positive, HER2-negative breast cancer and 1-3 positive axillary lymph nodes (nodal stage N1), who had a Recurrence Score of 0-25. This trial did not include pre and postmenopausal women with Recurrence Score results 26-100, based on previously published studies suggesting that this patient group benefited from chemotherapy.

SWOG S1007 (RxPONDER) is an multicenter, international, prospective, randomized, Phase III trial, in which patients with HR-positive, HER2-negative breast cancer with 1-3 positive axillary lymph nodes were included, to determine which patients would benefit from chemotherapy and which patients could safely avoid it. In this study, a total of 5083 HR-positive, HER2-negative breast cancer patients with 1-3 positive lymph nodes and Oncotype DX Recurrence Score of less than 25 were randomly assigned 1:1 to receive chemotherapy plus endocrine therapy (N=2547) or endocrine therapy alone (N=2536). The median patient age was 57.5 years and approximately two-thirds of patients were postmenopausal and one-third were premenopausal and had no contraindications to taxane and/or anthracycline based chemotherapy. Patients were stratified by Recurrence Score (0-13 versus 14-25), menopausal status, and axillary nodal dissection versus sentinel node biopsy. The Primary endpoint was Invasive Disease Free Survival (IDFS), defined as local, regional, or distant recurrence, any second invasive cancer, or death from any cause, and whether the effect depended on the Recurrence Score. Secondary endpoints included distant Relapse Free Survival (RFS) and Overall Survival (OS).

At a median follow up of 6.1 years, the chemotherapy benefit with respect to increasing invasive DFS differed according to menopausal status. Among postmenopausal women, in this updated analysis with longer follow up, the invasive DFS at 5 years was 91.9% in the endocrine therapy alone group, and was 91.3% in those treated with chemotherapy plus endocrine therapy (HR=1.02; P=0.89). Postmenopausal women with recurrence scores of 0 to 25 continued to NOT benefit from adjuvant chemotherapy.

Among premenopausal women however, the invasive DFS at 5 years was 89% in the endocrine therapy alone group and 93.9% % in those treated with chemotherapy plus endocrine therapy (HR=0.64; P=0.004). There was a 5-year absolute benefit of 4.9% for invasive DFS with chemotherapy among premenopausal women. There was a similar increase noted in the distant Relapse Free Survival (HR=0.58; P=0.009). The relative chemotherapy benefit did not increase as the Recurrence Score increased.

It was concluded from this practice-changing study that postmenopausal women with HR-positive, HER2-negative breast cancer with 1-3 positive nodes and Oncotype DX Recurrence Score of 25 or less, can safely avoid receiving adjuvant chemotherapy, whereas premenopausal patients with 1-3 positive nodes and a Recurrence Score of 25 or less benefited from chemotherapy plus endocrine therapy and had a longer invasive Disease Free Survival and distant Relapse Free Survival, than those who received endocrine therapy alone.

21-Gene Assay to Inform Chemotherapy Benefit in Node-Positive Breast Cancer. Kalinsky K, Barlow WE, Gralow JR, et al. N Engl J Med 2021;385:2336-2347

POLIVY® in Previously Untreated Diffuse Large B-Cell Lymphoma

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SUMMARY: The American Cancer Society estimates that in 2021, about 81,560 people will be diagnosed with Non Hodgkin Lymphoma (NHL) in the United States and about 20,720 individuals will die of this disease. Diffuse Large B-Cell Lymphoma (DLBCL) is the most common of the aggressive Non-Hodgkin lymphoma’s in the United States, and the incidence has steadily increased 3-4% each year. More than half of patients are 65 or older at the time of diagnosis and the incidence is likely to increase with aging of the American population. The etiology of Diffuse Large B-Cell Lymphoma is unknown. Contributing risk factors include immunosuppression (AIDS, transplantation setting, autoimmune diseases), UltraViolet radiation, pesticides, hair dyes, and diet.

DLBCL is a neoplasm of large B cells and the most common chromosome abnormality involves alterations of the BCL-6 gene at the 3q27 locus, which is critical for germinal center formation. Two major molecular subtypes of DLBCL arising from different genetic mechanisms have been identified, using gene expression profiling: Germinal Center B-cell-like (GCB) and Activated B-Cell-like (ABC). Patients in the GCB subgroup have a higher five year survival rate, independent of clinical IPI (International Prognostic Index) risk score, whereas patients in the ABC subgroup have a significantly worse outcome. Regardless, R-CHOP regimen (Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone), given every 21 days, for 6 cycles, delivered with curative intent, is the current standard of care for patients of all ages, with newly diagnosed DLBCL, regardless of molecular subtype. Approximately 30-40% of patients experience disease progression or relapse, during the first 2 years and attempts to improve on R-CHOP regimen have not been successful. Maintenance treatment strategy following R-CHOP, to better control the disease, delay disease progression and improve long term survival, have included Autologous Stem Cell Transplantation, maintenance treatment with agents such as oral protein kinase inhibitor Enzastaurin and Everolimus. Outcomes for transplant-ineligible patients with Relapsed/Refractory DLBCL patients remain poor.

CD79b is a B-cell specific surface protein, which is a component of the B-cell receptor and is ubiquitously expressed on the surface of malignant B cells. POLIVY® (Polatuzumab vedotin) is a CD79b-directed Antibody-Drug Conjugate (ADC) with activity against dividing B cells. It consists of three components: 1) the humanized ImmunoGlobulin G1 (IgG1) monoclonal antibody specific for human CD79b; 2) the small molecule anti-mitotic agent MMAE (monomethyl auristatin E) and 3) a protease-cleavable linker that covalently attaches MMAE to the Polatuzumab antibody. Upon binding to CD79b, POLIVY® is internalized, and the linker is cleaved by lysosomal proteases thus enabling intracellular delivery of MMAE. MMAE then binds to microtubules and kills dividing cells by inhibiting cell division and inducing apoptosis. POLIVY® demonstrated efficacy in patients with Relapsed or Refractory DLBCL, resulting in significantly longer Overall Survival when combined with Bendamustine and Rituximab, compared to Bendamustine and Rituximab alone. Based on these finding, the FDA granted accelerated approval to POLIVY® in June 2019.

In a Phase Ib-II study POLIVY® in combination with Rituximab, Cyclophosphamide, Doxorubicin, and Prednisone (pola-R-CHP) resulted in a 89% Overall Response rate and 77% Complete Responses when given as first line therapy, in patients with DLBCL. In this study, Vincristine was excluded from the regimen owing to the risk of overlapping neurotoxicities with POLIVY®. The present POLARIX trial was conducted to evaluate the efficacy and safety of pola-R-CHP as compared with R-CHOP, in patients with previously untreated DLBCL.

The POLARIX is a randomized, double-blind, placebo-controlled, International Phase III trial in which a total of 879 treatment naïve, CD20-positive, intermediate or high-risk DLBCL patients were randomly assigned in a 1:1 ratio to receive 6 cycles of either pola-R-CHP (N=440) or R-CHOP (N=439). Patients on Day 1 of each 21 day cycle, received POLIVY® 1.8 mg/kg IV and a placebo matching Vincristine IV (pola-R-CHP group) or a placebo matching POLIVY® and intravenous Vincristine at a dose of 1.4 mg/m2 (maximum of 2 mg) (R-CHOP group), along with Rituximab 375 mg/m2 IV, Cyclophosphamide 750 mg/m2 IV and Doxorubicin 50 mg/m2 IV. All the patients also received Prednisone 100 mg orally once daily on Days 1-5 of each of the first six cycles. During cycles 7 and 8, patients in both treatment groups received Rituximab monotherapy at 375 mg/m2 IV. The median patient age was 65 years and stratification was based on IPI score and presence or absence of bulky disease, Subtypes of DLBCL were centrally evaluated and were balanced between the two treatment groups. Patients were eligible regardless of the Cell of Origin or the presence of rearrangements in MYC, BCL2, BCL6, or a combination of these. Patients with known CNS involvement were excluded but CNS prophylaxis with intrathecal chemotherapy was permitted, in accordance with institutional practice guidelines. The use of Granulocyte Colony-Stimulating Factor (G-CSF) was required during the first six cycles of treatment for primary prophylaxis against neutropenia and consolidative radiotherapy to initial sites of bulky disease or extranodal sites was allowed at the discretion of the investigator. The Primary end point was Progression Free Survival (PFS). Secondary end points included Overall Survival (OS) and Safety.

At a median follow up of 28.2 months, the PFS was significantly higher in the pola-R-CHP group compared to the R-CHOP group. The PFS at 2 years was 76.7% in the pola-R-CHP group versus 70.2% in the R-CHOP group (stratified HR=0.73; P=0.02). Treatment with pola-R-CHP resulted in a risk of disease progression, relapse, or death that was 27% lower, compared to R-CHOP. Patient subgroups that did not show a clear benefit with pola-R-CHP included patients 60 years of age or younger, patients with the Germinal Center B-cell-like subtype of DLBCL, patients who had bulky disease, and patients who had lower IPI scores. Overall Survival at 2 years did not differ significantly between the treatment groups and the researchers attributed the lack of a significant difference between the two groups in Overall Survival, to the availability of new, effective treatments for relapsed or refractory DLBCL, as well as short duration of follow up at the time of this reporting. The safety profile was similar in the two treatment groups.

The authors concluded that among patients with previously untreated intermediate-risk or high-risk DLBCL, the risk of disease progression, relapse, or death was lower among those who received pola-R-CHP than among those who received R-CHOP.

Polatuzumab Vedotin in Previously Untreated Diffuse Large B-Cell Lymphoma. Tilly H, Morschhauser F, Sehn LH, et al. December 14, 2021. DOI: 10.1056/NEJMoa2115304

Late Breaking Abstract – ESMO 2021: Adjuvant KEYTRUDA® for High Risk Stage II Melanoma

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SUMMARY: The American Cancer Society’s estimates that for 2021, about 106,110 new cases of melanoma will be diagnosed in the United States and 7,180 people are expected to die of the disease. The rates of melanoma have been rising rapidly over the past few decades, but this has varied by age.

Surgical resection with a curative intent is the standard of care for patients with early stage melanoma, with a 5-year survival rate of 98% for Stage I disease and 90% for Stage II disease. The current standard of care for patients following resection of high-risk Stage II disease is observation, even though patients with Stage IIB and IIC disease presenting with high-risk features (depth of invasion, T-category, ulceration) have 5 and 10 year melanoma-specific survival similar to that of patients with Stage IIIA and IIIB disease.

KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2. By doing so, it unleashes the tumor-specific effector T cells, and is thereby able to undo PD-1 pathway-mediated inhibition of the immune response. The FDA in 2019, approved KEYTRUDA® for the adjuvant treatment of patients with melanoma, with involvement of lymph node(s) following complete resection (Stage III). The present study was conducted to evaluate the role of adjuvant immunotherapy in patients with high risk Stage II melanoma.

KEYNOTE-716 is a randomized, double-blind, Phase III trial, in which 976 patients aged 12 years or older, with completely resected cutaneous Stage IIB or IIC melanoma, and no lymph node involvement, were randomly assigned 1:1 to receive KEYTRUDA® 200 mg (2 mg/kg for pediatric patients) or placebo, every 3 weeks for 17 cycles (up to 1 year). Patients were stratified by T category 3b, 4a, 4b (adults) and with a separate stratum for pediatric patients. Approximately 65% had Stage IIB disease and 35% had Stage IIC disease. There was no prespecified analysis for PD-L1 or BRAF status in this study, as there was inconsistent and small amounts of tissue available for testing. This was the first part (Part 1) of this double-blind study. The Primary endpoint was Relapse Free Survival (RFS) per investigator assessment, and Safety. The second part (Part 2) of this study was open-label design, and adults and pediatric patients were eligible to receive up to 35 additional cycles of treatment, only if they had recurrence after receiving the placebo or completed 17 cycles of KEYTRUDA®. Patients in the KEYTRUDA® group who experienced disease recurrence within 6 months of completing the treatment were excluded from Part 2 of the study. Secondary end points included Distant Metastasis-Free Survival, Overall Survival (OS) and Quality of Life. The researchers herein reported the results at the interim analysis of Part 1 of this study, and Part 2 data are not yet mature.

At median follow up of 14.4 months, the study met its Primary end point of RFS at the first protocol-specified analysis. KEYTRUDA® significantly prolonged RFS compared to placebo (HR=0.65; P=0.00658). At the time of this analysis, 11.1% of patients on KEYTRUDA® had a recurrence, compared to 16.8% of those receiving placebo. The 12-month RFS rate was 90.5% for KEYTRUDA® versus 83.1% for placebo. Median RFS was Not Reached in either group at the time of this analysis. Quality of Life scores were similar between the KEYTRUDA® and placebo groups at all time points.

It was concluded that adjuvant KEYTRUDA® for resected Stage IIB and IIC melanoma decreased the risk of disease recurrence or death by 35% compared with placebo, and was associated with significantly prolonged Relapse Free Survival and a favorable benefit-risk profile. KEYNOTE-716 is the first randomized Phase III trial of an anti-PD-1 therapy in resected Stage II melanoma, and these findings represent an important milestone for this patient group.

LBA3_PR – Pembrolizumab versus placebo after complete resection of high-risk stage II melanoma: Efficacy and safety results from the KEYNOTE-716 double-blind phase III trial. Luke JJ, Rutkowski P, Queirolo P, et al. Annals of Oncology (2021) 32 (suppl_5): S1283-S1346. 10.1016/annonc/annonc741.

Late Breaking Abstract – ESMO 2021: Keytruda® Plus Chemotherapy in Advanced Cervical Cancer

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SUMMARY: The American Cancer Society estimates that for cervical cancer in the US for 2021, about 14,480 new cases of invasive cervical cancer will be diagnosed and about 4,290 women will die of the disease. Cervical pre-cancers are diagnosed far more often than invasive cervical cancer. Cervical cancer is most frequently diagnosed in women between the ages of 35 and 44 and in the US. Hispanic women are most likely to develop cervical cancer, followed by African-Americans, Asians and Pacific Islanders, and whites.

Patients with persistent, recurrent, or metastatic cervical cancer often receive Platinum-based chemotherapy, (Cisplatin or Carboplatin along with Paclitaxel) plus Bevacizumab. The addition of Bevacizumab to chemotherapy improved the median Overall Survival from 13.3 months to 17 months in a randomized study.

KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2. It thereby reverses the PD-1 pathway-mediated inhibition of the immune response and unleashes the tumor-specific effector T cells. In the KEYNOTE-158 trial, the Objective Response Rate (ORR) with single agent KEYTRUDA® in previously treated recurrent or metastatic cervical cancer patients with PD-L1 positive tumors was 14.3%. KEYNOTE-826 trial was conducted to assess whether adding KEYTRUDA® to Platinum-based chemotherapy with or without Bevacizumab would improve efficacy, as compared with chemotherapy with or without Bevacizumab, as first line therapy for persistent, recurrent, or metastatic cervical cancer.

KEYNOTE-826 is a global, multicenter, double-blind, randomized Phase III trial, in which 617 women with recurrent, persistent, or metastatic cervical cancer were randomly assigned in a 1:1 ratio to receive KEYTRUDA® 200 mg IV or placebo, every 3 weeks for up to 35 cycles. Patients in both treatment groups received Paclitaxel 175 mg/m2 IV and the investigator’s choice of Cisplatin 50 mg/m2 or Carboplatin AUC 5 IV every 3 weeks. Chemotherapy was limited to 6 cycles, although patients with ongoing clinical benefit without unacceptable side effects could continue beyond 6 cycles. Bevacizumab at a dose of 15 mg/kg IV every 3 weeks was allowed at the investigator’s discretion. Enrolled patients were not previously treated for advanced disease and were not considered curable. The median patient age was 50 years, and close to two thirds of the patients had persistent or recurrent disease with distant metastases. Patients were stratified according to metastatic disease at diagnosis, planned Bevacizumab use and PD-L1 Combined Positive Score (CPS) less than 1, 1-9 and 10 or more. All the treatment groups were well balanced and about 63% of patients in each treatment group received Bevacizumab. Eighty eight percent (88%) of patients had PD-L1 CPS 1 or more at baseline, and 51% had CPS 10 or more. Approximately 72% of the patients had Squamous Cell Carcinoma, 56% received previous chemoradiotherapy with or without surgery, and 20% had previously untreated metastatic disease at trial entry. The dual Primary endpoints were Progression Free Survival (PFS) and Overall Survival (OS). The median follow up for the first interim analysis was 22.0 months.

The median PFS in those patients with a PD-L1 CPS of 1 or more (N=548) was 10.4 months in the KEYTRUDA® group and 8.2 months in the placebo group (HR for disease progression or death=0.62; P<0.001). This represented a 38% reduction in the risk of disease progression or death in the KEYTRUDA® group. The PFS in all enrolled patients (N=617) was 10.4 months and 8.2 months, respectively (HR=0.65; P<0.001). The PFS in patients with a PD-L1 CPS of 10 or more (N=317) was 10.4 months and 8.1 months, respectively (HR=0.58; P<0.001).

The OS at 24 months was significantly longer in the KEYTRUDA® group, compared to the placebo group, among patients with a PD-L1 CPS of 1 or more, and was 53% in the KEYTRUDA® group and 41.7% in the placebo group (HR for death= 0.64; P<0.001), 50.4% and 40.4% among all enrolled patients (HR=0.67; P<0.001), and 54.4% and 44.6% among patients with a PD-L1 CPS of 10 or more (HR=0.61; P=0.001), respectively. The confirmed Response Rates were also higher and Duration of Response longer in all patient groups receiving KEYTRUDA®, compared to placebo. Side effects with the combination therapy were manageable and were as expected, based on known adverse events with the individual drugs.

It was concluded that the addition of KEYTRUDA® to chemotherapy, with or without Bevacizumab, significantly prolonged Progression Free and Overall Survival, among patients with persistent, recurrent, or metastatic cervical cancer.

Pembrolizumab for Persistent, Recurrent, or Metastatic Cervical Cancer. Colombo N, Dubot C, Lorusso D, et al. for the KEYNOTE-826 Investigators. September 18, 2021. DOI: 10.1056/NEJMoa2112435.

Late Breaking Abstract – ESMO 2021: ENHERTU® Superior to KADCYLA® in Patients with HER2 Positive Metastatic Breast Cancer

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SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. Approximately 284,200 new cases of breast cancer will be diagnosed in 2021 and about 44,130 individuals will die of the disease, largely due to metastatic recurrence.

The HER or erbB family of receptors consist of HER1, HER2, HER3 and HER4. Approximately 15-20% of invasive breast cancers overexpress HER2/neu oncogene, which is a negative predictor of outcomes without systemic therapy. Patients with HER2-positive metastatic breast cancer are often treated with anti-HER2 targeted therapy along with chemotherapy, irrespective of hormone receptor status, and this has resulted in significantly improved treatment outcomes. HER2-targeted therapies include HERCEPTIN® (Trastuzumab), TYKERB® (Lapatinib), PERJETA® (Pertuzumab) and KADCYLA® (ado-Trastuzumab emtansine). Dual HER2 blockade with HERCEPTIN® and PERJETA® given along with chemotherapy (with or without endocrine therapy), as first line treatment, in HER2 positive metastatic breast cancer patients, was shown to significantly improve Progression Free Survival (PFS) as well as Overall Survival (OS). The superior benefit with dual HER2 blockade has been attributed to differing mechanisms of action and synergistic interaction between HER2 targeted therapies. Patients progressing on Dual HER2 blockade often receive KADCYLA® which results in an Objective Response Rate (ORR) of 44% and a median PFS of 9.6 months, when administered after HERCEPTIN® and a taxane. There is however no standard treatment option for this patient population following progression on KADCYLA®.

ENHERTU® (Trastuzumab Deruxtecan) is an Antibody-Drug Conjugate (ADC) composed of a humanized monoclonal antibody specifically targeting HER2, with the amino acid sequence similar to Trastuzumab, a cleavable tetrapeptide-based linker, and a potent cytotoxic Topoisomerase I inhibitor as the cytotoxic drug (payload). ENHERTU® has a favorable pharmacokinetic profile and the tetrapeptide-based linker is stable in the plasma and is selectively cleaved by cathepsins that are up-regulated in tumor cells. Unlike KADCYLA®, ENHERTU® has a higher drug-to-antibody ratio (8 versus 4), released payload easily crosses the cell membrane with resulting potent cytotoxic effect on neighboring tumor cells regardless of target expression, and the released cytotoxic agent (payload) has a short half-life , thus minimizing systemic exposure.

In the DESTINY-Breast 01 Phase II registration trial involving patients with HER2-positive metastatic breast cancer, who had received two or more prior HER2 targeted therapies including KADCYLA®, the Objective Response Rate (ORR) was 60.9%, with 6% Complete Responses and 54.9% Partial Response, with a median response duration of 14.8 months. The median PFS was 16.4 months. This benefit was consistent across all key subgroups, including patients who had previously received PERJETA® therapy.

DESTINY-Breast 03 is a global, multicenter, open-label, randomized Phase III study, in which the efficacy and safety of ENHERTU® was compared with KADCYLA®, in patients with HER2-positive metastatic breast cancer previously treated with Trastuzumab and a Taxane. In this study, 524 pts were randomized 1:1 to receive ENHERTU® 5.4 mg/kg (N=261) or KADCYLA® 3.6 mg/kg (N=263) once every 3 weeks. The median patient age was 54 years and patients in both treatment groups were comparable in terms of baseline characteristics including age, HER2-positivity status, ECOG Performance Status, prior treatment for breast cancer, brain metastases, and prior cancer therapy with agents including Trastuzumab. The Primary endpoint was Progression Free Survival (PFS) by Blinded Independent Central Review (BICR). Secondary endpoints include Overall Survival (OS), Objective Response Rate (ORR), Duration of Response, PFS by investigator, and Safety.

At the time of the prespecified interim analysis of this study, the median follow up was approximately 16 months and the median PFS by BICR review was Not Reached with ENHERTU® and was 6.8 months with KADCYLA® (HR=0.28; P= 7.8 × 10−22). This represented a very statistically significant 72% reduction in the risk for progression or death with ENHERTU® compared to KADCYLA®. The investigator-assessed PFS was similar (25.1 versus 7.2 months, HR=0.26, P<0.0001). This PFS benefit was observed as early as 4 weeks and remained consistent throughout the follow up period. PFS was significantly higher with ENHERTU® in all prespecified key subgroups, including Hormone Receptor status, prior treatment with PERJETA®, visceral disease, number of prior lines of therapy, and the presence or absence of brain metastases. Majority of patients in the ENHERTU® group experienced a reduction in tumor size, and the ORR was significantly higher among patients in the ENHERTU® compared to those who received KADCYLA® (79.7% versus 34.2%; P<0.0001), with a near doubling of the Complete Response rate in the ENHERTU® group, at 16.1% compared to 8.7% in the KADCYLA® group. The estimated 12-month Overall Survival rate was 94.1% versus 85.9% respectively (HR=0.56; P=0.007), but was not considered significant as it did not cross the prespecified boundary for significance, likely due to the immaturity of the dataset.

Adjudicated treatment related Interstitial Lung Disease/pneumonitis was more common in the ENHERTU® compared with the KADCYLA® treatment arm, at rates of 10.5% and 1.9%, respectively and most of the events were Grade 1 or 2 in severity, and none at Grade 4 or 5 in either treatment group. Interstitial Lung Disease profile was of less concern, than was seen in previous trials of ENHERTU® in more heavily pretreated patients. All Left Ventricular Ejection Fraction decreases were Grade 1 or 2 and were seen in 2.7% of the ENHERTU® group and in 0.4% of KADCYLA® group.

The researchers concluded that ENHERTU® demonstrated a highly statistically significant and clinically meaningful improvement in Progression Free Survival, when compared to KADCYLA®, in patients previously treated with Trastuzumab and Taxane for HER2-positive metastatic Breast cancer, with manageable toxicity and a significant improvement in Interstitial Lung Disease profile. The authors added that these data support ENHERTU® becoming the standard of care for second line treatment of HER2-positive metastatic breast cancer.

Trastuzumab deruxtecan (T-DXd) vs trastuzumab emtansine (T-DM1) in patients (Pts) with HER2+ metastatic breast cancer (mBC): Results of the randomized phase III DESTINY-Breast03 study. Cortés J, Kim SB, Chung WP, et al. Presented at: European Society for Medical Oncology 2021 Virtual Congress. September 16-21, 2021; virtual. Abstract LBA1.

KEYTRUDA® in Combination with Chemotherapy Improves Overall Survival in Triple Negative Breast Cancer

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SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. Approximately 284,200 new cases of breast cancer will be diagnosed in 2021 and about 44,130 individuals will die of the disease, largely due to metastatic recurrence. Triple Negative Breast Cancer (TNBC) is a heterogeneous, molecularly diverse group of breast cancers and are ER (Estrogen Receptor), PR (Progesterone Receptor) and HER2 (Human Epidermal Growth Factor Receptor-2) negative. TNBC accounts for 15-20% of invasive breast cancers, with a higher incidence noted in young patients. It is usually aggressive, and tumors tend to be high grade and patients with TNBC are at a higher risk of both local and distant recurrence. Those with metastatic disease have one of the worst prognoses of all cancers with a median Overall Survival of 13 months. The majority of patients with TNBC who develop metastatic disease do so within the first 3 years after diagnosis, whereas those without recurrence during this period of time have survival rates similar to those with ER-positive breast cancers.

The lack of known recurrent oncogenic drivers in patients with metastatic TNBC, presents a major therapeutic challenge. It appears that there are subsets of patients with TNBC who may be inherently insensitive to cytotoxic chemotherapy. Three treatment approaches appear to be promising and they include immune therapies, PARP inhibition and inhibition of PI3K pathway. Previously published studies have shown that presence of tumor-infiltrating lymphocytes was associated with clinical benefit, when treated with chemotherapy and immunotherapy, in patients with TNBC, and improved clinical benefit was observed in patients with immune-enriched molecular subtypes of metastatic TNBC.

KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2. It thereby reverses the PD-1 pathway-mediated inhibition of the immune response, and unleashes the tumor-specific effector T cells. The rationale for combining chemotherapy with immunotherapy is that cytotoxic chemotherapy releases tumor-specific antigens, and immune checkpoint inhibitors such as KEYTRUDA® when given along with chemotherapy can enhance endogenous anticancer immunity. Single agent KEYTRUDA® in metastatic TNBC demonstrated durable antitumor activity in several studies, with Objective Response Rates (ORRs) ranging from 10-21% and improved clinical responses in patients with higher PD-L1 expression. When given along with chemotherapy as a neoadjuvant treatment for patients with high-risk, early-stage TNBC, KEYTRUDA® combination achieved Pathological Complete Response rate of 65%, regardless of PD-L1 expression. Based on this data, KEYTRUDA® in combination with chemotherapy was studied, for first line treatment of advanced TNBC.

KEYNOTE-355 is a randomized, double-blind, Phase III study, which evaluated the benefit of KEYTRUDA® in combination with one of the three different chemotherapy regimens, nab-Paclitaxel, Paclitaxel, or the non-taxane containing Gemzar/Carboplatin, versus placebo plus one of the three chemotherapy regimens, in patients with previously untreated or locally recurrent inoperable metastatic TNBC. In this study, 847 patients were randomized 2:1 to receive either KEYTRUDA® 200 mg IV on day 1 of each 21-day cycle along with either nab-Paclitaxel 100 mg/m2 IV on days 1, 8 and 15 of each 28-day cycle, Paclitaxel 90 mg/m2 IV on days 1, 8 and 15 of each 28-day cycle, or Gemcitabine 1000 mg/m2 IV plus Carboplatin AUC 2, IV on days 1 and 8 of each 21-day cycle (N= 566) or placebo along with one of the three chemotherapy regimens (N= 281). This study was not designed to compare the efficacy of the different chemotherapy regimens. Treatment was continued until disease progression. Patients were stratified by chemotherapy, PD-L1 tumor expression (CPS of 1 or higher versus CPS of less than 1), and prior treatment with the same class of neoadjuvant/adjuvant chemotherapy (Yes versus No). The baseline characteristics of treatment groups were well-balanced. The co-Primary end points of the trial were Progression Free Survival (PFS) and Overall Survival (OS) in patients with PD-L1-positive tumors, and in all patients. Secondary end points were Objective Response Rate (ORR), Duration of Response, Disease Control Rate, and Safety.

The authors had previously reported that KEYTRUDA® in combination with chemotherapy, significantly improved PFS in patients with CPS (Combined Positive Score) of 10 or greater. The median PFS was 9.7 months for KEYTRUDA® plus chemotherapy, compared with 5.6 months for placebo plus chemotherapy (HR=0.65, P=0.0012). This represented a 35% reduction in the risk of disease progression. Among patients with CPS of 1 or greater, the median PFS was 7.6 months for KEYTRUDA® plus chemotherapy, compared with 5.6 months for the placebo plus chemotherapy arm (HR= 0.74; P=0.0014). This however based on prespecified statistical criteria, was not considered statistically significant. Among the entire Intention-To-Treat (ITT) population, the median PFS was 7.5 months in the KEYTRUDA® plus chemotherapy group, compared with 5.6 months for chemotherapy plus placebo group (HR=0.82).

The researchers have now reported the Overall Survival results after a median follow up of 44.1 months. The OS in the subgroup of patients with PD-L1 CPS of 10 or more was significantly better with first line KEYTRUDA® plus chemotherapy versus placebo plus chemotherapy (23.0 months versus 16.1 months, respectively; HR=0.73; P=0.0093). This represented a 27% reduction in the risk of death with the KEYTRUDA® combination. Among this subgroup, factors significantly associated with superior outcomes included age 65 yrs and older, use of Paclitaxel as the on-study chemotherapy, no prior adjuvant therapy, de novo metastasis, Disease Free Interval of 12 months or more, and less than 3 metastatic sites. However, this OS benefit was not noted in the subgroup of patients with PD-L1 CPS scores of 1 or less. In this subgroup, the median OS was 17.6 months in the KEYTRUDA® group and 16 months in the placebo group (HR=0.86; P=Not Significant). The same was true among the Intention-To-Treat (ITT) population, including all randomized patients regardless of PD-L1 tumor status. In this patient group, the median OS was 17.2 months in the KEYTRUDA® group and 15.5 months in the placebo group, and this was not statistically significant (HR=0.89).

The authors concluded that these updated results support KEYTRUDA® in combination with chemotherapy as a new standard-of-care treatment regimen for patients with locally recurrent unresectable or metastatic Triple Negative Breast Cancer, whose tumors express PD-L1, with CPS of 10 or more.

KEYNOTE-355: Final results from a randomized, double-blind phase 3 study of first-line pembrolizumab + chemotherapy vs placebo + chemotherapy for metastatic TNBC. Cortes J, Cescon DW, Rugo HS. et al. European Society for Medical Oncology (ESMO) Annual Meeting 2021: Abstract LBA16. Presented on September 19, 2021.