Prolonged Diagnostic Pathways and Advanced-Stage Presentation in Early-Onset Colorectal Cancer: A Mexican Cohort Study.

Background Early-onset colorectal cancer (EOCRC) (diagnosed before age 50) is rising worldwide, with the steepest increases in rectal and distal colonic tumors and a disproportionate burden in Latin American populations. Because young patients are diagnosed through symptoms rather than screening, they often present with advanced disease; yet the diagnostic pathway that precedes this presentation - and whether delay shapes stage - remains uncharacterized in Mexico. We aimed to quantify the diagnostic and treatment pathway of Mexican patients with EOCRC and to examine its association with advanced-stage presentation. Methods Single-center, retrospective, cross-sectional study of patients younger than 50 years with histopathologically confirmed adenocarcinoma of the colon or rectum managed at a tertiary referral center in Mexico City (January 2016-June 2026). Diagnostic intervals were reconstructed from the medical record using the Aarhus framework. Advanced stages were clinical stages III-IV. Groups were compared (Mann-Whitney U; χ²/Fisher), and multivariable logistic regression identified factors associated with advanced stage; we compared patients with and without computable intervals and performed a sensitivity analysis in those diagnosed from 2019 onward. Results Among 226 patients (median age 41 years (IQR 35-45); 91 (40%) aged <40 years; 118 (52%) male), tumors were located in the rectum in 121 (54%). Advanced stages (III-IV) were present in 176/226 (78%). The median total interval from symptom onset to treatment was 243 days (IQR 142-407); 72/108 (67%) exceeded 180 days, and the diagnostic interval exceeded 90 days in 51/141 (36%). Delay intervals did not differ between advanced- and early-stage disease (all p > 0.33), a finding confirmed in a sensitivity analysis restricted to patients diagnosed from 2019 onward. The advanced stage was independently associated with rectal location (adjusted OR 2.97, 95% CI 1.52-5.78; p = 0.001) and higher carcinoembryonic antigen (CEA) at diagnosis (p < 0.001). Conclusions Young Mexican patients with EOCRC present overwhelmingly with advanced disease after markedly prolonged diagnostic pathways (median ~8 months). Although delay was not statistically associated with stage, the high burden of advanced presentation and rectal predominance highlights an actionable gap in early recognition and timely referral.