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In a comprehensive review of SEER (Surveillance, Epidemiology, and End Results) 18 data researchers analyzed histologic colorectal subtypes independently and found that some lesions categorized as colorectal cancer may potentially be lower-risk tumors. The findings are published in
Annals of Internal Medicine.
Data indicate that adenocarcinomas are increasing in most early-onset subgroups, but that carcinoids, a distinct type of tumor, are increasing at a faster rate, at least in part because of increased detection and case capture by cancer registries.
Researchers from Tulane University Medical Center reviewed SEER 18 data from 2000 to 2016 for 119,624 patients with colorectal cancer to assess early-onset colorectal cancer incident rates and changes in incident rates over time, stratified by histologic subtype (primarily adenocarcinoma and carcinoid tumors). Adenocarcinoma is key to analyze because it is a target for prevention through screening programs and risk factor stratification (for example, earlier screening for patients with a family history of cancer). The researchers found that 4% to 20% of colorectal cancers were carcinoid tumors as opposed to adenocarcinoma, a proportion that had increased over time. In the rectum, the colonic segment with the largest reported increase in early-onset CRC, up to 34% of lesions depending on patient age, were carcinoid tumors rather than adenocarcinoma in the most contemporary period. This is significant because carcinoid tumors have a distinct pathogenesis from adenocarcinomas.