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© F EN G Y U ; C R YS TA L LI G H T / S H U TT ER ST O C K .C O M E arly-onset colorectal cancer (CRC), which occurs before the age of 50 years, has been on the rise in the United States for several decades and appears to be increasing the fastest in Western states according to a study published in the Journal of the National Cancer Institute.1 The study, conducted by the American Cancer Society and The Ohio State University, analyzed changes in CRC incidence and risk factors among adults younger than 50 years from 1995 to 2015 on the basis of state and race/ethnicity. By examining geographic differences, researchers hoped to uncover new clues about what may be driving the trend. Investigators found that early-onset CRC increased by 1.1% per year from 2006 to 2015. The incidence of rectal tumors rose faster than that of colon tumors (1.7% vs 0.7% per year). Researchers also found that the increase was mostly confined to whites, with average increases exceeding 2.5% per year in 10 states, 6 of which are in the West. For example, CRC incidence during the entire decade increased by 73% in Washington and by 57% in Colorado. According to researchers, the findings indicate that more study needs to be done on the causes of early-onset CRC. The disease is often associated with risk factors such as obesity, physical inactivity, and smoking, and its incidence rates are lower in the West in comparison with other regions such as the South. However, the fact that rates are increasing the most sharply in the West suggests that unknown early-life exposures, in addition to established risk factors, may be contributing to the equation, says lead author Rebecca Siegel, MPH, the scientific director of surveillance research at the American Cancer Society. “Future studies should explore novel risk factors for colorectal cancer in young adults,” she says.