The incidence of second primary cancer in male and female patients with initial colorectal cancer: a SEER population-based study.

BACKGROUND: Second primary cancer (SPC) after primary colorectal cancer (CRC), emerges as a novel challenge for cancer prevention with pronounced differences between female and male patients. METHODS: This was a retrospective study of 140 907 CRC survivors from the surveillance, epidemiology, and end results program database. Competing risk models and nomograms were constructed to predict the risk of SPCs, which were assessed with the C-Index, calibration and decision curve analysis. RESULTS: The 10-year cumulative incidence of SPC was higher in male than in female CRC survivors. The top five common SPCs in female CRC survivors were colorectal, breast, lung and bronchus, corpus and uterus and pancreatic cancers, while in male were prostate, colorectal, lung and bronchus, urinary cancer and melanoma of the skin. Breast and prostate were the most common sites for the development of SPCs after CRC. Older age, stage I and surgery were common risk factors for SPCs in both female and male. The nomogram for predicting the risk of developing SPC-breast cancer in female patients included age, race, site, histology grade, surgery, chemotherapy and stage. However, the model of predicting SPC-prostate cancer in male patients included age, race, site, size, surgery, chemotherapy, radiation and stage. Notably, the nomograms were validated to have a precise discriminative ability, accuracy and clinical effectiveness. CONCLUSIONS: The study surveyed the characteristics of CRC survivors with a particular focus on the incidence of SPC. The models could help supervise the development of a second breast or prostate cancer in female or male CRC survivors.