Sex variation in colorectal cancer mortality: trends and implications for screening

Background: Colorectal cancer (CRC) screening using faecal tests reduces disease-specific mortality. To investigate mortality and its association with sex, rates in women and men, and in different age ranges, were examined, before and after screening began in Scotland.

Methods: From 1990-1999, no structured screening existed. Three pilots ran from 2000-2007 and subsequent full roll-out completed in 2009. Crude mortality rates for 1990-2020 were calculated relative to Scottish population estimates, and age-sex standardised rates calculated for all, pre-screening (<50 years), screening (5-74 years), and post-screening (>74 years) age ranges.

Results: CRC mortality declined from 1990-2020, but not linearly, and differed between sexes. In women, 1990-1999 showed a steady decline (average annual percentage change: AAPC): AAPC: -2.1%, 95% CI: -2.8% to -1.4%), but a less marked decline after 2000 (AAPC: -0.7%, 95% CI: -0.9% to -0.4%). In men, no clear decline was seen from 1990-1999 (AAPC: -0.4%, 95% CI: -1.1% to 0.4%), but mortality declined from 2000-2020 (AAPC: -1.7%, 95% CI: -1.9% to -1.5%). This pattern was exaggerated in the screening age ranges. For 2000-2020, the overall reduction in mortality was less in women and in the screening age range. In the post-screening age range, reductions were smaller but an increase was seen in the pre-screening age range, greater in women.

Conclusions: CRC mortality fell during 1990- 2020, but the decline differed markedly between sexes, indicating a larger beneficial effect of screening on CRC mortality in men compared to women: use of different thresholds for the sexes might lead to equality.