Prospective study of treatment pattern, effectiveness, and safety of zoledronic acid (ZOL) therapy beyond 24 months subgroup analysis of patients (pts) with metastatic bone disease (MBD) from breast cancer (BC)

SUMMARY:There is not much data on the effectiveness and safety of Zoledronic acid (ZOMETA®) beyond 2 years. Two studies one from Belgium and the other from Japan shed some light on this issue. In the prospective multicenter Belgian trial, 108 women with breast cancer prior to enrollment had received at least 24 months of therapy with ZOMETA® infusions given every 3 to 4 weeks and 21% had received at least 48 months of therapy. They were followed for 18 months and monitored for Skeletal Related Events (SRE’s), Osteo Necrosis of the Jaw bone (ONJ), renal failure and hypocalcemia. During this follow up period, SRE’s were low and 83% of the women were free of SRE’s. ONJ was seen in 7 patients (4.5%). The rate of ONJ however rose to 11% after any invasive dental procedure. The risk of renal failure was low but increased to 12%when the dose of ZOMETA® was not adjusted for renal function. The Japanese study was a retrospective analysis of 83 patients who had been treated with ZOMETA® for at least 24 months (median 33 months). SRE’s were low and the frequency of ONJ was 3.6% compared to 2.4% for those patients who had been ZOMETA® for shorter periods. Both these studies demonstrated that longer duration of therapy with ZOMETA® resulted in increased rate of ONJ. Therefore, particular attention should be paid to prevent this complication by adhering to proper dental hygiene and avoiding dental trauma and extractions. Van den Wyngaert T, Delforge M, Doyen C, et al. and Suzuki Y, Saito Y, Ogiya R, et al. CTRC-AACR San Antonio Breast Cancer Symposium 2012; Poster P3-13-01 and P3-13-02.