Healthier pre-diagnosis lifestyle and long-term survival in colorectal cancer: Evidence from the Singapore Chinese Health Study

BACKGROUND: Evidence from Western populations suggests that healthier pre-diagnosis lifestyles are associated with improved relative survival after colorectal cancer. We quantified the survival differences by composite pre-diagnosis lifestyle. METHODS: Incident colorectal cancer cases (n=2124) were identified from the Singapore Chinese Health Study via registry linkage. Deaths (all-cause and colorectal cancer-specific) through December 2022 were ascertained. Pre-diagnosis lifestyle (diet, physical activity, smoking, BMI, sleep) was assessed at enrolment (1993-1998) and combined into a composite score. Cox models estimated hazard ratios (HRs); restricted mean survival time (RMST) quantified absolute differences at 10 years post‑diagnosis. Models were adjusted for stage, age at diagnosis, sex, education, alcohol, and the interval from enrolment to diagnosis. RESULTS: During a median of 4.8 years (IQR 1.2-11.8) of follow-up, 1557 all-cause deaths occurred, including 1103 colorectal cancer-specific deaths. Patients with high versus low pre-diagnosis lifestyle scores had lower hazards of all-cause (HRadjusted 0.74 (95%CI 0.65-0.92)). The adjusted 10-year RMST difference (high-minus-low) for all-cause mortality was 0.85 years (95%CI 0.34-1.35). In patients aged ≤70 years (n=922), the associations were similar with a 10-year RMST difference of 1.15 years (0.35 to 1.95). Stage dominated outcomes with a 10‑year RMST difference (late-minus-early) of -3.33 years (-3.72 to -2.93). CONCLUSIONS: While stage at diagnosis remains the principal driver of survival for patients with colorectal cancer, healthier pre-diagnosis lifestyles were associated with modest improvements in long‑term survival. IMPACT: Longitudinally collected behaviours at multiple time points will complement our findings, providing stronger evidence on the health behaviours that support better survivorship.