LAUSR

Background: The utilization of bilateral (B/L) mastectomy for ductal carcinoma in situ (DCIS) has been rising within the last two decades. This is occurring despite the lack of convincing evidence to support the positive impact of this approach on disease-specific or overall survival (OS.) Notably, the estimated annual risk of developing a contralateral breast cancer is only 0.1% per year. Method: This is a retrospective cohort analysis of National Inpatient Sample database between the years 2005 and 2014 of adult females who underwent B/L mastectomy. ICD-9-CM procedure codes were used to identify two subpopulations; those who had only DCIS without invasive breast cancer or high risk genetic syndrome (DCIS mastectomy) and all others. The aim of this study is to assess the demographic predictors of undergoing B/L mastectomy for DCIS. Statistical analysis done using STATA. Results: The total number of B/L mastectomies performed within the study period was 144,754, of which 24,766 (17.1%) were performed for DCIS with no invasive cancer and no high risk genetic syndrome. There was no significant difference between the two groups in age (average 52.8 years), length of stay (average 2.34 days) and total charge for hospitalization (average $51,209). Among DCIS mastectomy patients, 56.3% were >50 year-old and only 0.7% were 18-30 year-old, 80.7% were Caucasian and 7.5% were African American, 42% were from highest income quartile neighborhoods and 12.6% were from lowest income quartile neighborhoods and 77.8% had private insurance while 15.9% and 5.2% had Medicare and Medicaid, respectively. Interestingly, 95.6% of B/L mastectomies for DCIS were performed at urban centers, 63.6% in teaching hospitals and 64.2% were in large hospital by bed size. Univariate regression showed no significant predictive value for undergoing B/L mastectomy for DCIS indication by age, race, hospital geographic region, teaching status of hospital or hospital size. The odds of undergoing B/L mastectomy for DCIS was higher for age category for 30-50 year-old compared to 18-30 year-old (OR=2.6, p Conclusion: A significant proportion of B/L mastectomies are being performed for DCIS. While this approach has not convincingly yielded an OS benefit, it has significant clinical and psychological morbidity along with considerable financial toxicity. We found inequity in populations that receive this procedure by age, race, insurance status, income quartile and urban or rural location of center. Further studies would be helpful to delineate this disparity among patients and assess the utility of B/L mastectomy in the era of molecular prediction and superior therapeutic modalities. Citation Format: Sindhu Janarthanam Malapati, Sunny RK Singh, Rohit Kumar, Jason Mouabbi, Ahmed Abdalla, Carrie Dul, Tarik Hadid. Bilateral mastectomy in ductal carcinoma in situ: 10-year analysis of national inpatient sample database [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-08-04.