SUMMARY: ColoRectal Cancer (CRC) is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates that approximately 135,430 new cases of ColoRectal Cancer will be diagnosed in the United States in 2017 and over 50,260 patients are expected to die of the disease. The lifetime risk of developing ColoRectal Cancer is about 1 in 20 (5%).
Even though the incidence of Colorectal cancer (CRC) in the United States has been rapidly declining overall, primarily driven by screening, the incidence however has been increasing among adults younger than age 50 years. To understand this trend, the authors in this publication conducted a retrospective cohort study among 490,305 patients aged 20 years and older, who were diagnosed with colorectal cancer between 1974 and 2013, using data from nine oldest Surveillance, Epidemiology, and End Results (SEER) registries. The SEER program is considered the gold standard for cancer registration worldwide because of the high quality of data and is the only source for historical population-based cancer incidence in the United States. This study included people born in 1890 thru 1990. Colorectal cancer incidence trends were analyzed by 5-year age group and birth cohorts.
The authors noted variations in CRC incidence patterns by age, tumor location in the colon, calendar period, and birth cohort. The study found that in adults aged 20-39 years, after a decrease in the previous decade, colon cancer incidence rates increased by 1.0-2.4% per year since the mid-1980s thru 2013. For adults aged 40-54 years during the same period, colon cancer incidence rates increased by 0.5-1.3%. Conversely, from the mid-1980s thru 2013, colon cancer rates declined in adults aged 55 years and older. In adults younger than age 50 years, there was an increasing trend for tumors to be confined to the distal colon, with the exception of adults aged 40-49 years, among whom there was an also an increasing trend for proximal tumors.
The incidence of rectal cancer has been increasing even longer and faster than colon cancer, rising about 3.2% per year from 1974-2013 in adults aged 20-29 years and from 1980-2013 in adults aged 30-39 years. In adults aged 40 to 54, rectal cancer rates increased by 2.3% per year from the 1990s to 2013. Again, rectal cancer rates declined, in adults aged 55 years and older, from 1974-2013.
Compared with adults born around 1950, those born around 1990 had double the risk of colon cancer and quadruple the risk of rectal cancer. The increase in the incidence of CRC in young adults has been attributed to western style, high carbohydrate, high fat, low fiber diet which can initiate inflammation and proliferation in the colonic mucosa within two weeks. Other lifestyle factors associated with CRC include obesity, high consumption of processed meat and alcohol, low levels of physical activity and cigarette smoking. Further, young patients are 58% more likely than older patients to be diagnosed with advanced versus localized stage CRC, due to delayed follow-up of symptoms, sometimes for years and these young adults are less likely to be screened for colon cancer, despite their symptoms.
The authors concluded that there is an increasing rate of colon and rectal cancer among young and middle-aged adults in the US and compared with adults born around 1950 when the risk was at the lowest, those born around 1990 have double the risk of colon cancer and quadruple the risk of rectal cancer. They added that as nearly a third of rectal cancer patients are younger than age 55 years, screening initiation before age 50 years should be considered. Colorectal Cancer Incidence Patterns in the United States, 1974-2013. Siegel RL, Fedewa SA, Anderson WF, et al. J Natl Cancer Inst. 2017 Aug 1;109(8). doi: 10.1093/jnci/djw322.
