Abstract B59: Bilateral oophorectomy at age 55 or older does not reduce risk of breast cancer

Abstract Introduction: It is widely accepted that premenopausal bilateral oophorectomy (BSO) reduces the risk of breast cancer. However, recently published data suggest that BSO done after menopause may also reduce risk of breast cancer. We sought to determine the impact of postmenopausal BSO on subsequent breast cancer diagnosis in a nationally representative sample. Methods: The National Health Interview Survey (NHIS) is a population-based survey conducted annually by the CDC and is designed to be representative of the non-institutionalized civilian population in the United States. We utilized data from the 2010 NHIS cancer supplement to compare breast cancer diagnosis rates in women who underwent postmenopausal BSO versus those who did not. We defined our population of interest as those women ages 65 and older who underwent BSO between the ages of 55-64. Statistical analyses were conducted using SUDAAN software. Results: In 2010, 21707 women ages 65 and older were surveyed, representing 190,813,389 people in the population. Of these, 0.97% underwent BSO between the ages of 55-64. 4.82% of women 65 years of age and older were surveyed reported developing breast cancer after the age of 65. On univariate analysis, 8.08% of women who had undergone a BSO between the ages of 55-64 developed breast cancer after age 65; whereas 24.11% of women who had not undergone a BSO developed breast cancer after age 65 (p=0.0188). The median age at which women undergoing BSO developed cancer was 74 years, on average 14 years after their oophorectomy. Having a BSO after menopause (vs. not having a BSO) was not associated with age of menarche 11 years or younger (13.8% vs. 15.6%, p=0.3701), parity (91.9% vs. 89.2%, p=0.3793), age at first live birth < 20 (22.5% vs. 34.3%, p=0.0125), family history of a first degree relative with breast cancer (p=0.3726), body mass index 30 or above (31.6% vs. 28.2%, p=0.2811), income (p=0.2819), region (p=0.1811) or race/ethnicity (p=0.7611). However, BSO was found to be associated with higher education levels (p=0.0461), Medicare insurance (98.1% vs. 95.4%, p=0.0002) and increased ever use of HRT (50.3% vs. 25.6%, p= 0.0008). Controlling for these potential confounders on multivariate analysis, BSO was no longer associated with breast cancer after age 65 (OR = 0.38; 95% CI: 0.10-1.43, p=0.1522). Conclusion: Bilateral oophorectomy performed in women after the age of 55 does not appear to reduce the risk of postmenopausal breast cancer. This patient population should continue to be counseled on other methods to reduce breast cancer risk, such as chemoprevention and weight loss. Citation Format: Erin Hofstatter, Anees Chagpar. Bilateral oophorectomy at age 55 or older does not reduce risk of breast cancer. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr B59.