["Several studies have shown that contralateral prophylactic mastectomy (CPM) provides a disease-free and overall survival (OS) benefit in young women with estrogen receptor (ER)-negative breast cancer. We utilized the National Cancer Data Base to evaluate CPM's survival benefit for young women with early -stage breast cancer in the years that ER status was available.", 'We selected 14,627 women ≤45 years of age with American Joint Committee on Cancer stage I-II breast cancer who underwent unilateral mastectomy or CPM from 2004 to 2006. Five-year OS was compared between those who had unilateral mastectomy and CPM using the Kaplan-Meier method and Cox regression analysis.', 'A total of 10,289 (70.3 %) women underwent unilateral mastectomy and 4,338 (29.7 %) women underwent CPM. Median follow up was 6.1 years. After adjusting for patient age, race, insurance status, co-morbidities, year of diagnosis, ER status, tumor size, nodal status, grade, histology, facility type, facility location, use of adjuvant radiation and chemohormonal therapy, there was no difference in OS in women <45 years of age who underwent CPM compared towith those who underwent unilateral mastectomy (hazard ratio [HR] = 0.93; p = 0.39). In addition, Tthere was no improvement in OS in women <45 years of age with T1N0 tumors who underwent CPM versus unilateral mastectomy (HR = 0.85; p = 0.37) after adjusting for the aforementioned factors. Among women ≤45 years of age with ER-negative tumors who underwent CPM, there was no improvement in OS compared with women who underwent unilateral mastectomy (HR = 1.12; p = 0.32) after adjusting for the same aforementioned factors.'] Does contralateral prophylactic mastectomy provide no survival benefit in young women with estrogen receptor-negative breast cancer?