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Yes, Early Onset Colorectal Adenocarcinoma Rates Are Increasing, But Rectal Carcinoid Rates Are Increasing Faster

Douglas K. Rex, MD, MASGE, reviewing Montminy EM, et al. Ann Intern Med 2020 Dec 15.

There is now widespread recognition that there are increasing rates of colorectal cancer in persons under age 50 (early-onset colorectal cancer), that most of the increases are attributable to cancer in the distal colon and rectum, and that the etiology of the increasing rates is unknown. Previous studies have commonly used population-based data derived from SEER (surveillance, epidemiology, and end results) data that combine adenocarcinoma and carcinoid to form combined colorectal cancer incidence. The current study reports colorectal cancer divided into the subtypes of adenocarcinoma and carcinoid.

The study confirms that incidence rates of adenocarcinoma are increasing in young people. The steepest rises have occurred in rectal-only cases in persons aged 20 to 29 years and 30 to 39 years and colon-only cases in those aged 30 to 39 years. In 40- to 49-year-olds, adenocarcinoma incidence is increasing in both the colon and rectum. Absolute incidence rates of adenocarcinoma are still very age-dependent. 

Remarkably, rates of carcinoid tumors are increasing at a faster rate than adenocarcinoma rates, although the incidence is confined mostly to the rectum, except in 50- to 54-year-olds, for whom a significant increase in carcinoids was also found in the colon. The absolute increase in the rectal carcinoid rate in 50- to 54-year-olds over a 15-year interval was 159%. The contribution of carcinoid tumors to overall colorectal cancer incidence rates increased substantially over the 15-year interval from 18% to 26% in 20- to 29-year-olds and 11% to 23% in 50- to 54-year-olds.

Douglas K. Rex, MD, FASGE


It would be interesting to learn how all these rectal carcinoid tumors came to medical attention since rectal carcinoids have a limited tendency to metastasize or produce symptoms. In any case, the data suggest colonoscopists should keep their eyes peeled for carcinoid tumors in young patients, particularly in the rectum, and remove them endoscopically or surgically as appropriate for their size.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.


Montminy EM, Zhou M, Maniscalco L, et al. Contributions of adenocarcinoma and carcinoid tumors to early-onset colorectal cancer incidence rates in the United States. Ann Intern Med 2020 Dec 15. (Epub ahead of print) (

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