Population incidence and characteristics of secondary breast cancer after uterine cancer: a competing risk analysis

To examine incidence and characteristics of women who developed secondary breast cancer after uterine cancer.This is a population-based retrospective cohort study utilizing the National Cancer Institute's Surveillance, Epidemiology, and End Result Program from 1973 to 2013. Women with uterine cancer who did not have synchronous or a history of breast cancer were followed after their uterine cancer diagnosis (N = 236,561). A time-dependent competing risk analysis was performed to examine cumulative incidences and clinico-pathological characteristics of those who subsequently developed breast cancer.There were 7110 (3.0%) women who developed secondary breast cancers after uterine cancer with 5-, 10-, and 20-year cumulative incidence rates of 1.5, 2.8, and 4.7%, respectively. The increase in the rate of secondary breast cancer was particularly high in the first 3 years after a uterine cancer diagnosis (annual percent change [APC] 4.9), followed by 3-7 years (APC 1.6) after diagnosis (P 0.001). The median time to develop secondary breast cancer was 6.4 years. Older women had significantly shorter time intervals between uterine and breast cancer diagnoses (3.7 years for aged 71, 5.9 for aged 64-71, 7.6 for aged 56-63, and 9.4 for aged 56, P 0.001). In a multivariable analysis, older age, White race, married status, endometrioid, serous, and mixed histology types, and early-stage tumors remained as independent factors of developing secondary breast cancer (all, P 0.05).Tumor factors with endometrioid and serous histology types and early-stage disease were the factors associated with secondary breast cancer after uterine cancer diagnosis. Older women had shorter time to develop secondary breast cancer.