A colorectal cancer rate in U.S. registry data rose in 2023 after more than two decades of decline, prompting researchers to call for continued monitoring as they investigate what changed.
The study analyzed records from 21 registries run through the National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results (SEER) program. Together, the registries cover 45.8% of the U.S. population. The age-adjusted incidence rate was 55.2 cases per 100,000 people in 2000, then fell to 36.7 in 2022 before reaching 38.3 in 2023. The study said no earlier annual increase appears in the series, which began in 2000.
The change varied by age. A University of Chicago Medicine summary said rates rose among groups through ages 65 to 69, then leveled off among people 70 to 74. People ages 45 to 49 had the steepest annual rise, at 12.76% from 2019 through 2023.
Researchers said expanded screening may have contributed to the increase among 45- to 49-year-olds. In 2021, the U.S. Preventive Services Task Force (USPSTF) lowered the recommended screening start age for average-risk adults from 50 to 45. Caitlin Murphy, a University of Chicago professor of pediatrics and public health sciences, said screening is “catching cancer earlier.” Researchers said screening does not explain the overall increase or rises in other age groups.
A 2026 American Cancer Society report found that from 2013 through 2022, incidence fell 2.5% a year among adults 65 and older, while it rose 3% among people 20 to 49 and 0.4% among those 50 to 64. Those figures use different periods and age groups from the new study, so they are not directly comparable.
The cause of the 2023 increase has not been established. University of Chicago Medicine said researchers plan to measure environmental exposures in blood samples and test candidate chemicals using organoids, lab-grown models of tissue. The planned work examines possible explanations; it does not establish that chemical exposure caused the rate change.
The university said a sustained increase could add demand for cancer treatment and survivorship care. Study authors called for continued monitoring as registry data are updated annually, providing further evidence on whether the rise persists.
