Bilateral Mastectomy as Overtreatment for Breast Cancer in Women Age Forty Years and Younger with Unilateral Operable Invasive Breast Cancer.

Background: Young women with breast cancer (BC) have an increased risk of contralateral breast cancer (CBC) compared with older women. This may contribute to the rising rates of bilateral mastectomy (BM), but it is unclear if BM leads to improved outcomes.

Methods: A prospectively maintained database was reviewed. Patient and tumor characteristics, survival, and rate of CBC were compared in women age ≤40 years treated for unilateral Stage 1-3 BC from January 2000 through December 2013.

Results: Patients ranged in age from 20 to 40 (mean 36) years. Of the 446 women, 188 had breast conservation surgery (BCS), 78 had unilateral mastectomy (UM), and 183 had BM. UM, BCS, and BM groups did not differ in mean age, tumor type, hormone receptor status, or Her2 status. Patients in the BCS and BM group had smaller, fewer node-positive (p = 0.02) and lower grade tumors (p < 0.01) compared with the UM group. With a median follow-up of 79 months, Disease-free survival was similar for patients treated with BM, BCS (p = 0.22), or UM (p = 0.75). OS was significantly worse in the patients treated with UM (0.02) but was not different between the BCS and BM groups. CBC incidence was 2% (5/263) in patients who underwent BCS or UM, and 0.4% (1/244) in patients without a germline genetic mutation.

Conclusions: BCS and UM resulted in similar disease-free survival (DFS) as BM in patients age 40 years and younger with BC. BCS and BM had similar OS, whereas UM patients had worse OS. Invasive CBC incidence was less than 0.5% at 10 years in patients without identified germline genetic mutations.