Trends in Early-Onset and Late-Onset Colorectal Cancer by Subtype in New York State, 1976-2022.

Background: Despite the steadily decreasing incidence rate of colorectal cancer (CRC) overall, many studies have reported increasing incidence of CRC among younger people (age < 50), early-onset colorectal cancer (EOCRC), in the United States. However, fewer studies have examined the trends by CRC subtype. We sought to better understand the trends of CRC incidence by subtype and age at diagnosis (particularly before age 50 versus age 50 or later) in recent decades in New York State and in other areas in the United States. Methods: Using the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) data, we estimated incidence rates of CRC for 11 subtypes, for different age groups, and by stage (local versus regional and distant) from 1976 through 2022 in New York State, compared with the same estimates from 2000 through 2021 in all 22 United States SEER cancer registries. All incidence rates are per 100,000 and age-adjusted to the 2000 United States standard population. Results: While the overall incidence rate of all CRC combined decreased for ages 50 and above from 229.5 in 1976-1980 to 106.3 in 2021-2022, it increased for ages under 50 from 5.9 to 10.0 during the same period. For ages under 50, the subtype-specific incidence rates increased for appendix (from 0.04 to 1.3), rectum (from 1.3 to 3.1), and sigmoid colon (from 1.2 to 2.1), while the other subtypes showed relatively low and steady incidence rates. For ages 50 and above, most subtypes showed generally decreasing incidence rates, with the exception of appendix, which steadily increased from 0.3 to 3.8. Data from the 22 registries combined showed almost identical trends. Conclusion: While aggregate statistics show increasing incidence rates of EOCRC, it is important to consider trends by CRC subtype. We observed that the increasing trends of EOCRC are primarily driven by appendix, rectum, and sigmoid colon cancers, and that the incidence rate of appendix cancer has been increasing across all age groups. Future studies should consider differences by subtype of CRC, as this information may help elucidate factors contributing to recent trends in EOCRC incidence.