Unmasking hidden trends: subsite-specific mortality patterns in colorectal and anal cancers in Spain, 1999-2023

To analyse long-term mortality trends in Spain (1999-2023) for four colorectal cancer (CRC) subsites-colon, rectosigmoid junction, rectum, and anus/anal canal-by sex, age, and birth cohort.

This ecological time-trend study used national mortality data from the Spanish National Statistics Institute, classified by ICD-10 codes C18-C21. Age-standardised mortality rates were calculated using the 2013 European Standard Population. Joinpoint regression estimated annual percentage changes, and age-period-cohort models evaluated generational and temporal effects.

Colon cancer mortality showed sex-specific patterns: a biphasic trend in men (initial rise, followed by decline) and a steady decrease in women. Rectal cancer mortality declined consistently in women, with a recent downward trend in men after years of stability. Mortality from rectosigmoid junction cancer remained relatively unchanged in both sexes. Anal cancer mortality increased steadily in men and, after an early decline, rose significantly in women, narrowing the sex gap. Mortality increased with age across all subsites, with men showing higher rates overall-except for anal cancer, where younger women's rates matched or surpassed those of men. Cohort analysis revealed generational declines in colon and rectal cancer mortality, contrasting with rising anal cancer risks, likely linked to increased HPV exposure. Period effects indicated notable mortality reductions for colon and rectal cancers but rising trends for anal cancer.

While mortality has declined for colon and rectal cancers, stagnation in rectosigmoid junction and rising anal cancer deaths-especially among women-underscore the need for subsite-specific prevention strategies, including HPV-targeted interventions.