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 151,030 new cases of CRC will be diagnosed in the United States in 2022 and about 52,580 patients are expected to die of the disease. The lifetime risk of developing CRC is about 1 in 23.
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 50 years of age, according to data in the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program. 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.
Based on benefits versus burden estimated by comparative modeling approaches using microsimulation models of CRC screening in a hypothetical cohort of 40-year-old US individuals, the American Cancer Society and the US Preventive Services Task Force within the past 4 years recommended lowering the age for screening initiation to 45 years for individuals at average risk. The recommended screening strategies include stool-based tests and endoscopic screening methods. Evidence from randomized clinical trials and prospective cohort studies has shown that endoscopic screening can reduce the incidence of and mortality from CRC, and endoscopic screening has the added advantage of CRC prevention by removal of precancerous lesions that could later become malignant, as well as detection of early-stage cancers that can be more effectively treated. There are however limited data with regards to the effectiveness of endoscopic screening in younger populations.
The authors conducted this prospective cohort study of lower gastrointestinal endoscopy (sigmoidoscopy or colonoscopy) among US female health professionals enrolled in the Nurses’ Health Study II between 1991 and 2017, to evaluate the association between endoscopy initiated at different ages and risk of CRC. The researchers also estimated the absolute risk reduction associated with endoscopy initiated at different ages through age 60 years. This analysis included 111,801 women, the median age was 36 years at the time of enrollment, and data analysis was performed from August 2020 to June 2021. The Primary end point of this study was overall CRC incidence. Secondary outcomes included incidence of younger-onset CRC (CRC diagnosed before 55 years of age) and CRC mortality.
The researchers noted that in the multivariable analysis after adjustment for age, family history, and lifestyle risk factors for CRC, compared with no endoscopy, women who underwent endoscopy had a significantly lower risk for incident colorectal cancer for age at initiation before 45 years (HR=0.37; 95% CI, 0.26-0.53), 45 to 49 years (HR=0.43; 95% CI, 0.29-0.62), 50 to 54 years (HR=0.47; 95% CI, 0.35-0.62), and 55 years or older (HR=0.46; 95% CI, 0.30-0.69).
The authors then estimated the multivariable-adjusted cumulative incidence of CRC and calculated the absolute risk reduction associated with each age group at endoscopy initiation. There was an absolute reduction in the estimated cumulative incidence of CRC through age 60 years, for women who initiated endoscopy between ages 45 to 49 years, compared with 50 to 54 years. Compared with no endoscopy, initiation of endoscopy before 50 years of age was also associated with a reduced risk of CRC diagnosed before 55 years of age (before age 45 years, HR=0.45; 95% CI, 0.29-0.70; 45-49 years, HR= 0.43, 95% CI, 0.24-0.76).
It was concluded that based on this analysis in a large, prospective cohort of women over a 26 year period, initiation of colorectal cancer screening before 50 years of age was associated with a reduced risk of CRC, and earlier initiation of endoscopy was associated with a greater absolute risk reduction of CRC, compared with initiation at later ages.
Age at Initiation of Lower Gastrointestinal Endoscopy and Colorectal Cancer Risk Among US Women. Ma W, MD, Wang M, Wang K, MD, et al. JAMA Oncol. Published online May 5, 2022. doi:10.1001/jamaoncol.2022.0883