Retrospective analysis of subsequent primary cancer risks among survivors of non-hereditary colorectal cancer

Colorectal cancer (CRC) survivors have increased risks of subsequent primary cancers (SPCs), but most studies have included individuals with hereditary CRC syndromes. A retrospective study using data from the Colon Cancer Family Registry Cohort (in Australia, Canada, and the United States) assessed SPC risks for CRC survivors without a known hereditary predisposition to CRC (so excluding individuals with pathogenic germline mutations in APC, MUTYH, or DNA mismatch repair genes). The study included 7202 CRC survivors (49.8% female, mean age at diagnosis 55.1 ± 11.5 years). The mean follow-up was 10.6 ± 7.45 years. Overall, there was no evidence of increased SPC risk (standardized incidence ratio 1.04; 95% CI 0.98-1.11). Elevated risks were observed for subsequent primary CRC, hematopoietic, liver, and thyroid cancer. Early onset CRC cases (diagnosed before age 50) had increased SPC risks (SIR 1.43; 95% CI 1.25-1.64) whereas those diagnosed at age 50 year and above did not (p<0.001). The authors conclude that in non-hereditary CRC survivors, overall SPC risks are not elevated, by early-onset cases have higher risks and therefore warrant targeted surveillance and follow-up.