Geographic and Ethnic Variation in Early-onset Colorectal Cancer: A Contemporary Scoping Review of Epidemiologic,...

Early-onset colorectal cancer (EOCRC), defined as diagnosis at ≤ 50 years, has shown rising incidence globally. However, geographic variation, molecular characteristics, and survival patterns remain heterogeneously reported. We conducted a scoping review to map contemporary evidence on epidemiologic, molecular, and survival differences in EOCRC across regions.

A scoping review was performed in accordance with PRISMA-ScR and Joanna Briggs Institute methodology. PubMed and Scopus were searched for studies published between January 2019 and March 2024. Eligible observational studies reported epidemiologic, molecular, or survival outcomes in EOCRC and included geographic or racial/ethnic stratification. Data were synthesized descriptively due to methodological heterogeneity.

Forty-six studies from 22 countries were included with evidence concentrated in Asia (n = 13) and North America (n = 13); Africa, Latin America, and South/Southeast Asia were markedly underrepresented. Across studies, EOCRC was more frequently associated with MSI/dMMR tumors (6.0-33.3%) and lower BRAF V600E prevalence than late-onset colorectal cancer (LOCRC) (typically 2.0-10.0%). Limited sequencing-based studies reported relative enrichment of CMS1 and CTNNB1 alterations in selected younger cohorts. Survival differences between EOCRC and LOCRC were heterogeneous across study populations, clinical settings, and reported endpoints. Some metastatic registry cohorts reported longer median overall survival among EOCRC patients, whereas advanced-stage disease was associated with poorer outcomes. Some studies also reported poorer outcomes among very-young EOCRC subgroups, although evidence for this association was limited and heterogeneous. Across studies reporting stage-specific outcomes, survival was consistently poorer with advanced-stage disease.

Contemporary evidence suggests that EOCRC differs from LOCRC in several reported molecular characteristics, whereas survival patterns remain heterogeneous and appear to be influenced primarily by stage at presentation. Geographic inequities in data availability and variability in molecular and survival reporting limit global generalizability. Standardized population-based studies from underrepresented regions are needed to clarify the relative contributions of tumor biology, stage distribution, and healthcare access to observed outcome differences.