239Incidence and potential risk factors of a second primary cancer among 217,702 colorectal cancer survivors

Abstract

Background Survival of colorectal cancer (CRC) has improved markedly but risk of an independent second primary cancer (SPC) increases. We determined incidence and potential risk factors of SPC following CRC. Methods We obtained data from 217,202 CRC cases (ICD-10 C18-C20, aged ≥20 years) diagnosed between 1990-2013 from the German Centre for Cancer Registry Data. Cancers arising in a distinct site (excluding non-melanoma skin cancer) and/or of a different histology group were classified as SPCs. Standardised incidence ratios (SIR) and 95% confidence intervals compared the excess risk to the general population, stratified by age, sex and CRC sub-site. Cox proportional hazards models identified potential risk factors of SPC. Results Following CRC (median age 70 years), 18,751 SPCs occurred (8.63%; median age 69 years). SPC incidence increased by 36% in males (SIR: 1.36 [1.34-1.38]), 46% in females (SIR: 1.46 [1.43-1.49]) and doubled for cases <65 years (SIR: 2.08 [1.99-2.17]). Common SPC sites following colon cancer included the small intestine, stomach, liver, pancreas, bladder and kidney. Common male-specific sites included prostate and in females: breast, uterus and ovary. Similar sites were observed following rectal cancer, particularly in cases <65 years. Age, male sex and tumour size (T1, T2) were potential risk factors of SPC. Therapy of CRC (including radiotherapy) did not demonstrate an elevated risk. Conclusions CRC survivors have an increased risk of SPC, particularly due to age, sex and tumour size. Key messages Colorectal cancer survivors have an increased risk of a SPC. Age, sex and tumour size are associated risk factors.