Abstract C020: Racial differences in the risks of second primary gynecologic cancers following chemotherapy for malignant ovarian tumors: Asian subgroups in the United States, 2000-2016
Authors: Mukand Nita H , Zolekar Ashwini N , Ko Naomi Y , Calip Gregory S 
Published: September 2020

Abstract
Objective: The incidence of ovarian cancer in the United States varies by race with the highest rates among white women but lower survival observed among black women and other racial and ethnic groups. These disparities in outcomes among women with ovarian cancer are not well understood, including the differential occurrence of second primary cancers according to race. Our objective was to measure racial differences in incidence of second primary gynecologic cancers (SPGC) among women with malignant ovarian tumors following treatment with chemotherapy. Specifically, we aimed to determine differences in SPGC incidence by Asian ethnic subgroups in the United States. Methods: We conducted a retrospective cohort study of women ages 20 years and older diagnosed with first primary malignant ovarian tumors treated with definitive surgery and chemotherapy between 2000 and 2016 from 18 population-based registries in the Surveillance, Epidemiology and End Results (SEER) Program. We collected demographic and clinical information on ovarian histologic subtypes, laterality, tumor grade, type of surgery and treatment with radiotherapy. Census tract-level sociodemographic characteristics of women were also described. The incidence of SPGC in our cohort was compared to expected incidence rates in the general population using age-and region-standardized incidence ratios (SIRs) and 95% confidence intervals (CI) for individual racial/ethnic groups. Results: Among 34,081 women with ovarian cancer, 74% were white, 6% were black, 8% were Asian/Pacific Islander (API) and 11% were Hispanic. Median age at diagnosis was lower among API and Hispanic women (54 years) compared to white (60 years) and black women (58 years). Most ovarian tumors were serous or endometrioid, although API women had a higher proportion of clear cell ovarian tumors (15%) compared to white (6%), black (5%) and Hispanic women (6%). Subgroups of API women also differed in distribution of ovarian tumor histology, grade, and age at diagnosis. Whereas incidence of SPGC was observed to be lower than expected among white women (SIR 0.72 CI 0.59-0.87), estimates were suggestive of higher than expected incidence among black (SIR 1.61, CI 0.88-2.71) and API women (SIR 1.64, CI 0.96-2.63), although confidence intervals included 1.0. Increased risk of vaginal cancers was observed among all women, although risk estimates were highest among API women (SIR 23.90, CI 4.93-69.84) and were also significant for risk of uterine cancers (SIR 2.28 CI 1.21-3.90). Among API women, only Filipinas had significantly increased incidence of SPGC overall including both uterine and vaginal cancers. Conclusions: Risk of SPGC following treatment of ovarian cancer differs by race. The increased incidence of secondary gynecological cancers observed in Asian women is driven largely by increased rates of uterine and vaginal cancers among Filipina women. Further research is warranted to understand the possible mechanism(s) underlying this observed disparity.
Citation Format: Nita H Mukand, Ashwini N Zolekar, Naomi Y Ko, Gregory S Calip. Racial differences in the risks of second primary gynecologic cancers following chemotherapy for malignant ovarian tumors: Asian subgroups in the United States, 2000-2016 [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr C020.