In a study reported in JAMA Network Open, Montminy et al found that the incidence of colorectal adenocarcinoma in people aged 40 to 49 years in the United States has increased in White individuals and remained stable in Black individuals between 2000 and 2017, with incidence rates being equivalent as of 2017. The incidence of rectal adenocarcinoma was markedly lower in the Black population, reflecting a disparity in incidence between White and Black women.
The cross-sectional study used 2000 to 2017 SEER 18 data on annual age-adjusted colorectal adenocarcinoma incidence rates among individuals aged 40 to 49 years, with analysis by Black and White race, anatomic subsite (colon or rectum), and sex. Annual percent change (APC) in incidence rates were determined.
Key Findings
The study included a total of 46,728 colorectal cancer cases in 45,429 patients. Among the patients, 6,480 (14.2%) were Black and 27,426 (60.4%) were White. Patients had a mean age of 45.5 ± 2.8 years.
Among White individuals aged 40 to 49 years, colorectal adenocarcinoma incidence rates increased from 19.6/100,000 person-years in 2000 to 25.2/100,000 person-years in 2017 (APC = 1.6, 95% confidence interval [CI] = 1.3–1.9). Among Black individuals aged 40 to 49 years, colorectal adenocarcinoma incidence rates did not significantly change—from 26.4/100,000 person-years in 2000 to 25.8/100,000 person-years in 2017 (APC = –0.03, 95% CI = –0.5 to 0.5). After 2013, colorectal adenocarcinoma incidence rates were no longer significantly higher among Black individuals vs White individuals.
Rectal-only absolute adenocarcinoma incidence rates in Black and White individuals were similar from 2000 to 2008 and significantly diverged beginning in 2009. Overall, annual percent change increased in White individuals (2.2, 95% CI = 1.6–2.8) and nonsignificantly decreased in Black individuals (–1.4, 95% CI = –2.6 to 0.1). Absolute incidence rates were 39% higher among White vs Black individuals by 2017. The study subgroups with the largest divergence in annual percent changes were White women (2.2, 95% CI = 1.6–2.8) vs Black women (–1.7, 95% CI = –3.6 to 0.3).
Absolute colon adenocarcinoma incidence rates remained higher in Black individuals during the entire 2000 to 2017 period, although annual percent change did not significantly change among Black individuals (0.5, 95% CI = –0.3 to 1.3) and increased among White individuals (1.2, 95% CI = 0.8–1.6).
The investigators concluded, “This study found that colorectal adenocarcinoma incidence rates in people aged 40 to 49 years were increasing among White individuals but stabilized among Black individuals, with absolute incidence rates becoming equivalent. Absolute rectal adenocarcinoma incidence rates were 39% lower in Black individuals, with a widening disparity in rectal cancer between White and Black women. Possible contributors include introduction of a screening threshold of age 45 years in Black individuals in 2008. Although the average-risk screening age has now shifted to age 45 years in all racial groups, these data can help motivate real-world implementation of guidelines to maximize screening rates that have historically been suboptimal in younger individuals.”
Jordan J. Karlitz, MD, of Denver Health Medical Center, University of Colorado School of Medicine, Denver, is the corresponding author for the JAMA Network Open article.
Disclosure: For full disclosures of the study authors, visit jamanetwork.com.
