Secondary ovarian cancer after external beam radiotherapy for nonovarian pelvic malignancy.

ABSTRACT

OBJECTIVE: To examine characteristics and survival of patients who developed secondary ovarian cancer after external beam radiotherapy (EBRT) for a prior nonovarian pelvic malignancy. METHODS: This is a population-based retrospective cohort study, querying the Surveillance, Epidemiology, and End Result program from 1975 to 2016. 167,269 women who received EBRT for 7 malignancies (anus, rectum, bladder, cervix, uterus, vulva, or vagina) were examined to identify subsequent secondary ovarian cancer diagnosis after EBRT. Then, within the ovarian cancer cohort (n = 147,618), characteristics and survival of patients with secondary ovarian cancer after EBRT were compared to those with ovarian cancer who did not receive prior EBRT. RESULTS: Following EBRT for a pelvic malignancy, 215 (1.3 per 1000) patients developed secondary ovarian cancer. Among those, the most frequent prior malignancy was cervical cancer (45.6%), followed by rectal cancer (20.9%). The median time from prior EBRT to secondary ovarian cancer was 8.8 years (interquartile range, 2.8-14.5). In multivariable analysis, patients with secondary ovarian cancer after EBRT were more likely to be older, and have a recent year of diagnosis, but less likely to have early-disease compared to ovarian cancer patients without prior EBRT (all, P < 0.05). In weighted model, patients with secondary ovarian cancer after EBRT had decreased overall survival compared to those with ovarian cancer without prior EBRT (5-year rates, 19.6% versus 39.9%, hazard ratio 1.62, 95% confidence interval 1.43-1.85). Similar association was observed in ages <70, ≥70, White, non-White, early-disease, and advanced-disease in sensitivity analyses. CONCLUSION: Radiotherapy-related secondary ovarian cancer may be associated with decreased overall survival.