The incidence of colorectal cancer (CRC) has declined steadily in persons over age 50 years of age, largely due to screening. In contrast, incidence rates have increased rapidly in younger adults (<50 years of age),1 raising the question of whether young-onset CRC is a distinct disease with unique biologic features or if it is the same disease occurring at a younger age. Studies comparing younger and older patients diagnosed with CRC have reported differences in clinical and molecular features, including tumor location, stage, and histology.2–6 However, increasing use of screening colonoscopy in the population has changed characteristics of CRC diagnosed over 50 years of age (eg, higher proportion now diagnosed with proximal tumors and/or at an earlier stage),7 so it is challenging to draw conclusions about the importance of these findings. To address this challenge, we compared characteristics of younger and older CRC patients in a predominantly unscreened population.
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