EP296/#298 Characteristics and outcomes of secondary ovarian cancer after external beam radiotherapy for female pelvic malignancy

Objectives

This study examined characteristics and survival of patients who developed secondary ovarian cancer after external beam radiotherapy (EBRT) that was prescribed for other female pelvic malignancies.

Methods

This is a population-based retrospective cohort study, querying the Surveillance, Epidemiology, and End Result program from 1975–2016. 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

Secondary ovarian cancer was identified in 215 (1.3 per 1,000) following EBRT. Cervical cancer was the most frequent diagnosis for prior EBRT (n=98, 45.6%) followed by rectal cancer (n=45, 20.9%). The median time from EBRT to secondary ovarian cancer diagnosis 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, have recent diagnosis year, and have advanced disease compared to ovarian cancer patients without prior EBRT (all, P<0.05). In a propensity score 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).

Conclusions

Although rare, secondary ovarian cancer can develop several years after EBRT for pelvic malignancy. Radiotherapy-related ovarian cancer may be associated with decreased survival outcome.