Abstract A55: Premenopausal gynecologic surgery and breast cancer mortality in the Carolina Breast Cancer Study

Introduction: In the United States, gynecologic surgery, including hysterectomy and oophorectomy, is frequently performed before menopause for benign conditions such as endometriosis, uterine fibroids, and ovarian cysts. Evidence has suggested that the prevalence of these procedures in the United States is far greater in Black women than in White women. Previous studies conducted in primarily White populations have shown that hysterectomy with bilateral oophorectomy reduces the risk of breast cancer mortality for women with breast cancer. The present study sought to evaluate the effect of premenopausal gynecologic surgery on breast cancer-specific and all-cause mortality in a population-based sample of Black and White women diagnosed with breast cancer. Methods: This study analyzed data from Phase 1 and Phase 2 of the Carolina Breast Cancer Study (CBCS). The CBCS is a population-based study that recruited Black and White women from 24 counties in central and eastern North Carolina between 1993 and 2001. Women with an incident invasive breast cancer diagnosis were identified using the North Carolina Central Rapid Case Ascertainment system. Information on gynecologic surgery was collected during nurse-administered in-person interviews, and women diagnosed with breast cancer with known surgical status were included in this analysis (n=1,723). Gynecologic surgery was operationalized in three categories: no surgery; hysterectomy with bilateral oophorectomy; hysterectomy with conservation of ≥ 1 ovary. Cause-specific mortality was ascertained using the National Death Index, last updated in 2011. Hazard ratios (HR) and 95% confidence intervals (CI) for breast cancer-specific and all-cause mortality were estimated with Cox Proportional Hazard Models. Multivariable HRs were adjusted for age at diagnosis, family history of breast cancer, smoking, alcohol use, hormone replacement therapy, and reproductive history factors. All participants still living at the end of follow-up were right censored. Models were weighted using the CBCS sampling fractions. Results: Among 1,723 women, there were 686 deaths of which 411 were from breast cancer. In this sample, 74.1% (n=1,276) of women reported having no gynecologic surgery, 8.8% (n=152) reported having had a hysterectomy with bilateral oophorectomy, and 17.1% (n=295) reported hysterectomy conservation of ≥ 1 ovary. Compared to women who had not had gynecologic surgery, the adjusted HR for breast cancer-specific mortality associated with hysterectomy and bilateral oophorectomy was 0.68 (95% CI: 0.48,0.94). In stratified models, HRs for breast cancer specific mortality were similar between White (HR=0.67, 95% CI: 0.43,1.0) and Black (HR=0.71, 95% CI: 0.38,1.22) women. No relationship was observed between hysterectomy with ovarian conservation and breast cancer survival. Estimated HRs for the association between hysterectomy with bilateral oophorectomy and all-cause mortality were in the opposite direction for Black (HR=0.73, 95% CI: 0.48,1.08) and White (HR=1.16, 95% CI: 0.93,1.44) women; however, these confidence intervals were wide and overlapping. Conclusions: This study supports prior evidence that hysterectomy with bilateral oophorectomy reduces the risk of breast cancer-specific mortality and this effect is consistent across White and Black women. The relationship between premenopausal gynecologic surgery and all-cause mortality in women diagnosed with breast cancer may potentially differ by racial group. Impact: Premenopausal gynecologic surgeries are very common in Black women diagnosed with breast cancer, but the effect of these surgeries on mortality was, to our knowledge, previously unknown in this population. Our findings add to the evidence base in understanding racial disparities in mortality after breast cancer more broadly. Citation Format: Mya Roberson, Whitney Ragan Robinson, Hazel Nichols, Andrew Olshan, Melissa Troester. Premenopausal gynecologic surgery and breast cancer mortality in the Carolina Breast Cancer Study [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr A55.