The influence of tumor side, sex, and screening on colon cancer stage and survival: a 25-year population-based study.

BACKGROUND: Screening policies eventually impact on colon cancer (CC) epidemiology. We evaluated the incidence trends of CC, its stage at diagnosis and related survival stratified by tumor location and demographics over 25 years across the adoption of FIT-based screening in a Northern Italy county. METHODS: The retrospective study analyzed 6697 CC cases from the tumor registry of the Parma County (1994-2018), spanning the introduction of programmatic screening in 2005. Annual percent changes in age-standardized incidence rates (ASRs) by tumor side, sex and age were assessed by Joinpoint and robust regression. The relationships of tumor side and demographics with tumor stage, screening status and overall survival were estimated by multivariable logistic regression and Cox proportional hazards models. RESULTS: In both sexes, the incidence of left-sided CC declined since the adoption of programmatic screening, within (p ≤ 0.001) and beyond (p ≤ 0.003) the screening age range. Differently, the incidence of right-sided CC did not, rather increased with aging (p ≤ 0.001). Beside older age (from 65 years; OR 1.39, 95% CI 1.05-1.82), right-sided CC was also independently associated with female sex (OR 1.40, 95% CI 1.27-1.54). Right-sided CC was diagnosed at more advanced stages in men (node-positive: OR 1.54, 95% CI 1.17-2.02; metastatic: OR 1.47, 95% CI 1.06-2.03), in whom also showed a worse prognosis (HR 1.16; 95% CI 1.01-1.34) than left-sided CC. CONCLUSIONS: Our results clarify the tight interplay between tumor side, sex, screening impact, stage and survival as descriptors of divergent CC behavior. Operational stratification of screening target populations by these descriptors can help improve and tailoring early diagnosis and prevention of CC.