Early-onset colorectal cancer (EOCRC) refers to colorectal cancer (CRC) diagnosed in adults younger than 50 years. We conducted this systematic review and meta-analysis to estimate EOCRC incidence, evaluate temporal trends from 1990 to 2021, identify factors associated with increased EOCRC risk, and project the anticipated burden through 2030. PubMed/MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched from inception through December 31, 2025. Population-based registry studies, cohort studies, and case-control studies reporting EOCRC incidence, temporal trends, or associated factors were included. The protocol was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO) (CRD420261345410). Two reviewers independently screened records, extracted data, and assessed study quality using the Newcastle-Ottawa Scale. Certainty of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework for the primary incidence estimate and the leading modifiable associated factors. Incidence rates and adjusted association estimates were pooled using random-effects meta-analysis, with analyses stratified by study design where appropriate. Prespecified subgroups included geographic region, sex, tumor subsite, Human Development Index stratum, calendar period, and age group; temporal trends were examined using meta-regression. Fifty-two studies from 52 countries were included. The pooled incidence showed substantial geographic variation, with the highest rates in Australasia and North America and the lowest rates in sub-Saharan Africa. Incidence increased significantly over time, with the Western Pacific showing the fastest rise. Rectal cancer increased more steeply than colon cancer. Family history of CRC and inflammatory bowel disease showed the strongest non-modifiable associations. Among modifiable exposures, sugar-sweetened beverages, processed meat consumption, obesity, Western dietary pattern, smoking, and alcohol use were associated with higher EOCRC odds. On current trajectories, EOCRC is projected to represent a growing share of CRC diagnoses by 2030. EOCRC is increasing across diverse geographic settings. These findings support clinical vigilance for alarm symptoms in younger adults, risk-stratified prevention, and public health strategies targeting modifiable lifestyle exposures.
Ahmad et al. (Mon,) studied this question.