Incidence, characteristics, and survival in early- and late-onset colorectal cancer.

Background and purpose: To study incidence changes, tumor characteristics, and relative survival (RS) among patients with early- (18-49 years) and late-onset (≥50 years) colorectal cancer (CRC). Patient/material and methods: In this retrospective registry study, all patients diagnosed with CRC in Finland between 1991 and 2015 were included and followed until death or the end of 2022. Data were extracted from the Finnish Cancer Registry. Changes in incidence as an average annual percentage change as well as age- and sex-standardized RS for CRC were estimated for 5-year periods between 1991-1995 and 2011-2015.

Results: The annual increase in incidence was higher for early-onset CRC versus late-onset CRC (1.2% vs. 0.44%), primarily due to an increase in left-sided colon cancer (2.0%) and rectal cancer (1.5%). Among 59,631 CRC patients, 3,988 (6.7%) had early-onset CRC, of whom 2,073 (52%) were female. Among 55,643 late-onset CRC patients, 27,796 (50%) were female. Among early-onset CRCs, 44% were right-sided, 19% left-sided, and 34% rectal compared with late-onset CRCs, of which 33% were right-sided, 23% left-sided, and 38% rectal. The 5-year RS for early-onset male patients improved from 64% to 72% and for female patients from 69% to 77%, whereas in late-onset patients, survival improved from 51% to 64% among males and from 52% to 67% among females.

Interpretation: The incidence of early-onset CRC is increasing more rapidly than for late-onset CRC. Overall, 5-year RS has improved and is higher in early-onset CRC patients compared with late-onset CRC.