Establishing a research agenda for early-onset colorectal cancer

Increases in early-onset CRC have been primarily driven by higher rates of rectal cancerEarly-onset CRC has not increased uniformly by anatomic sublocation.While rectal cancer incidence in younger adults increased from 3.0 per 100,000 in 1992 to 4.7 per 100,000 in 2015, there were smaller increases in proximal colon cancer during this period [12].Differences in incidence and distribution of early-onset CRC by sublocation underscore the importance of teasing apart risk factors for colon versus rectal cancer.Generally, risk factors fall into one of three categories: 1) decreased risk of colon cancer but no association with rectal cancer (e.g., dietary intake of folate and calcium); 2) increased risk of colon cancer but no association with rectal cancer (e.g., processed meat, family history); and 3) increased risk of both colon and rectal cancer (e.g., smoking, obesity) [18].Future etiological studies of early-onset CRC should examine risks separately-or how associations may be modified-by sublocation.