Purpose: Colorectal cancer (CRC) incidence has decreased over the past three decades, due largely to screening efforts. Relatively little is known about CRC incidence among the young adult (YA) population ages 20-39, as screening typically commences at age 50 for average-risk individuals. We examined CRC incidence with a focus on YAs in order to identify high-risk subgroups. Methods: We analyzed 231,544 incident CRC cases from 1988-2009 (including 5617 YAs 20-39 years of age) from the California Cancer Registry. We assessed age-specific incidence rates by race/ethnicity, gender, and colorectal tumor location, and calculated the biannual percent change (BAPC) to monitor change in incidence over the 22-year study period. Results: The absolute incidence of CRC per 100,000 was low among YAs 20-29 and 30-39 years old (ranging from 0.7 per 100,000 among Hispanic and African American females aged 20-29 up to 5.0 per 100,000 among Asian/Pacific Islander males aged 30-39). However, we observed increasing CRC incidence rates over time among both males and females in the YA population, particularly for distal colon cancer in Hispanic females aged 20-29 (BAPC=+15.9%; p<0.042). Conclusion: The absolute incidence of CRC remains far lower for YAs than among adults aged 50 and over. However, CRC incidence is increasing among young adults, in contrast to the decreasing rates observed for adults in the screened population (aged 50 and above). More research is needed to better characterize YAs at increased risk for CRC.
Keywords: CRC; colorectal cancer; health disparities; incidence; race/ethnicity; young adults.