Secondary Breast, Ovarian, and Uterine Cancers After Colorectal Cancer: A Nationwide Population-Based Cohort Study in Korea

BACKGROUND: The risk of a second primary cancer has increased along with the increasing life expectancies of colorectal cancer survivors. OBJECTIVE: We aimed to evaluate the incidence rate and risk factors of breast and gynecological (ovarian, uterine cervix/corpus) cancers among female colorectal cancer survivors. DESIGN: This is a retrospective population-based cohort study. SETTINGS: This study used data from the National Health Insurance Corporation of Korea. PATIENTS: Each patient with colorectal cancer diagnosed from 2007 to 2012 was followed until 2015 and compared with age-matched women without colorectal cancer at a 1:5 ratio. MAIN OUTCOME MEASURES: The primary outcome was de novo breast/gynecological cancer. Patients with available medical checkup data were included in an additional analysis. RESULTS: We analyzed 56,682 patients with colorectal cancer and 288,119 age-matched noncolorectal cancer controls. The risk of breast/gynecological cancer was higher among patients with colorectal cancer than among controls (HR, 2.91; p < 0.001). The association with colorectal cancer was the highest for ovarian cancer (HR, 6.72), followed by uterine corpus cancer (HR, 3.99), cervical cancer (HR, 2.82), and breast cancer (HR, 1.85). This association remained consistent in the subgroup analysis of medical checkup data (14,190 patients with colorectal cancer, 71,933 controls). Among patients with colorectal cancer, those aged <55 years had a higher risk of breast/gynecological cancers than those aged >55 years (HR, 3.51 vs 2.59), and those with dyslipidemia had a higher risk of breast cancer than those without dyslipidemia (HR, 2.66 vs 2.06). LIMITATIONS: This was a retrospective, population-based study. A prospectively designed study is needed to validate our conclusions. CONCLUSIONS: Compared with the general population, patients with colorectal cancer carry a higher risk of developing secondary breast, ovarian, and uterine cancers. See Video Abstract at http://links.lww.com/DCR/A731.