Young-onset colorectal cancer risk among individuals with iron-deficiency anaemia and haematochezia

Objective Young-onset colorectal cancer (YCRC) incidence is rising. Scant data exist on YCRC risk after presentation with concerning symptoms such as iron-deficiency anaemia (IDA) or haematochezia. We examined the association between IDA and YCRC, and haematochezia and YCRC. Design Cohort study of US Veterans aged 18–49 years receiving Veterans Health Administration (VHA) care 1999–2016. IDA analytic cohort was created matching individuals without incident IDA to those with IDA 4:1 based on sex, birth year and first VHA visit date (n=239 000). We used this approach to also create a distinct haematochezia analytic cohort (n=653 740). Incident YCRC was ascertained via linkage to cancer registry and/or cause-specific mortality data. We computed cumulative incidence, risk difference (RD) and HRs using Cox models in each cohort. Results Five-year YCRC cumulative incidence was 0.45% among individuals with IDA versus 0.05% without IDA (RD: 0.39%, 95% CI: 0.33%–0.46%), corresponding to an HR of 10.81 (95% CI: 8.15–14.33). Comparing IDA versus no IDA, RD was 0.78% for men (95% CI: 0.64%–0.92%) and 0.08% for women (95% CI: 0.03%–0.13%), and RD increased by age from 0.14% for Conclusion Colonoscopy should be strongly considered in adults aged