Contributions of Histologic Subtypes Tumors to Early-Onset Colorectal Cancer Incidence Rates

Published: December 15, 2020, in ACP Online, ACP Journals, Annals of Internal Medicine

Early-onset colorectal cancer (EOCRC) incidence rates (IRs) are rising, according to previous cancer registry analyses. However, analysis of histologic subtypes, including adenocarcinoma (the focus of CRC screening and diagnostic testing) and carcinoid tumors (which are classified as “colorectal cancer” in SEER [Surveillance, Epidemiology, and End Results] databases but have a distinct pathogenesis and are managed differently from adenocarcinoma), has not been reported.

The steepest changes in adenocarcinoma 3-year average annual IRs were for rectal-only cases in persons aged 20 to 29 years (+39% [0.33 to 0.46 per 100 000]; P < 0.050) and 30 to 39 years (+39% [1.92 to 2.66 per 100 000]; P < 0.050) and colon-only cases in those aged 30 to 39 years (+20% [3.30 to 3.97 per 100 000]; P < 0.050). These changes were driven by rectal subsites and were most pronounced in persons aged 50 to 54 years, in whom rectal carcinoid tumors increased by 159% (2.36 to 6.10 per 100 000) between 2000 to 2002 and 2014 to 2016, compared with 10% for adenocarcinoma (18.07 to 19.84 per 100 000), ultimately accounting for 22.6% of all rectal cancer cases.

These findings underscore the importance of assessing histologic CRC subtypes independently. Doing so may lead to a better understanding of the drivers of temporal changes in overall CRC incidence and a more accurate measurement of outcomes from efforts to reduce adenocarcinoma risk, and can guide future research.

This new research was published in the issue ACP Online, ACP Journals, Annals of Internal Medicine on December 15, 2020 with the title “Contributions of Adenocarcinoma and Carcinoid Tumors to Early-Onset Colorectal Cancer Incidence Rates in the United States. ” Contributors to this publication from the School of Public Health include two alumni Meijiao Zhou, MPH (Alumni), Lauren Maniscalco, MPH (Alumni) research staff in in the Louisiana Tumor Registry and Dr. Xiao-Cheng Wu, MD, MPH, Director of Louisiana Tumor Registry and faculty in Epidemiology. The authors and research team also included Eric M. Montminy, MD, Wesal Abualkhair, MD, Michelle Kang Kim, MD, Rebecca L. Siegel, MPH, Steven H. Itzkowitz, MD, Jordan J. Karlitz, MD.

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