Comparison of Survival After Breast-Conserving Therapy vs Mastectomy Among Patients With or Without the BRCA1/2 Variant in a Large Series of Unselected Chinese Patients With Breast Cancer

IMPORTANCE: Whether patients with breast cancer who carry a BRCA1/2 variant can safely undergo breast-conserving therapy (BCT) remains controversial. OBJECTIVE: To compare survival rates after BCT vs mastectomy in BRCA1/2 variant carriers and noncarriers in a large series of unselected patients with breast cancer. DESIGN, SETTING, AND PARTICIPANTS: In this cohort study, a large consecutive series of 8396 unselected patients with primary breast cancer underwent either BCT, mastectomy with radiotherapy, or mastectomy alone from October 1, 2003, to May 31, 2015, at the Breast Center of Peking University Cancer Hospital in China. All patients were assessed for BRCA1/2 germline variant status. Statistical analysis was performed from May 1 to September 30, 2020. MAIN OUTCOMES AND MEASURES: The primary outcomes were breast cancer–specific survival (BCSS) and overall survival (OS); secondary outcomes included recurrence-free survival, distant recurrence–free survival, and ipsilateral breast tumor recurrence. RESULTS: Of these 8396 Chinese patients (8378 women [99.8% women]; mean [SD] age, 50.8 [11.4] years; 187 BRCA1 carriers, 304 BRCA2 carriers, and 7905 noncarriers), 3135 (37.3%) received BCT, 1511 (18.0%) received mastectomy with radiotherapy, and 3750 (44.7%) received mastectomy alone. After a median follow-up of 7.5 years (range, 0.3-16.6 years), both BRCA1 and BRCA2 variant carriers treated with BCT had similar rates of survival compared with those treated with mastectomy with radiotherapy (BCSS: hazard ratio [HR] for BRCA1, 0.58 [95% CI, 0.16-2.10]; P = .41; HR for BRCA2, 0.46 [95% CI, 0.15-1.41]; P = .17; OS: HR for BRCA1, 0.61 [95% CI, 0.18-2.12]; P = .44; HR for BRCA2, 0.72 [95% CI, 0.26-1.96]; P = .52) or mastectomy alone (BCSS: HR for BRCA1, 0.70 [95% CI, 0.22-2.20]; P = .54; HR for BRCA2, 0.59 [95% CI, 0.18-1.93]; P = .39; OS: HR for BRCA1, 0.77 [95% CI, 0.27-2.21]; P = .63; HR for BRCA2, 0.62 [95% CI, 0.22-1.73]; P = .37) after adjusting for clinicopathologic factors and adjuvant therapy. For noncarriers, patients receiving BCT had significantly better survival than those receiving mastectomy with radiotherapy (BCSS: HR, 0.45 [95% CI, 0.36-0.57]; P < .001; OS: HR, 0.46 [95% CI, 0.37-0.58]; P < .001) or mastectomy alone (BCSS: HR, 0.71 [95% CI, 0.57-0.89]; P = .003; OS: HR, 0.71 [95% CI, 0.58-0.87]; P < .001) in multivariable analyses. CONCLUSIONS AND RELEVANCE: This study suggests that BRCA1/2 variant carriers treated with BCT have survival rates at least comparable to those treated with mastectomy with radiotherapy or mastectomy alone and that BCT could be an option for BRCA1/2 variant carriers when the tumor is clinically appropriate for BCT.