Long-Term Oncologic Outcome of Breast-Conserving Treatment in Patients With Breast Cancer With BRCA Variants.

Importance: Patients with sporadic breast cancer have comparable prognoses after undergoing either breast-conserving treatment (BCT) or mastectomy. However, there are limited and inconsistent data on the assessment of oncologic outcomes between BCT and mastectomy in patients with pathogenic variants in BRCA1 or BRCA2. Objective: To investigate the outcomes of BCT on recurrence and survival in patients with breast cancer with BRCA1 or BRCA2 pathogenic variants. Design, Setting, and Participants: This retrospective multicenter cohort study analyzed patients from 13 institutions in South Korea with primary breast cancer with BRCA1 or BRCA2 pathogenic variants who underwent either BCT or mastectomy from January 2008 through December 2015. The median (IQR) follow-up period was 8.3 (6.4-9.6) years. Data were analyzed from September 2023 to August 2024. Exposure: BRCA1 or BRCA2 pathogenic variant and BCT. Main Outcomes and Measures: Primary outcomes were logoregional recurrence-free survival, distant recurrence-free survival, and overall survival. Propensity score matching (PSM) using the greedy nearest neighbor method was performed to match covariates to minimize potential selection bias. Results: A total of 575 female patients with BRCA1 or BRCA2 pathogenic variants were identified, all of whom were South Korean with a mean (SD) age of 42.0 (9.7) years. Among them, 367 patients (66.2%) received BCT and 186 (33.8%) were treated with mastectomy. BCT was not a factor associated with oncologic outcomes, including locoregional recurrence, compared with mastectomy. After adjusting for clinicopathologic characteristics through 1:1 PSM, there were still no statistically significant differences in oncologic outcomes between the BCT group and the mastectomy group. Multivariate analysis showed that the type of breast surgery was not significantly associated with oncologic outcomes. In subgroup analysis among matched patients based on BRCA1 or BRCA2 status, tumor size, lymph node metastasis, histologic grade, and subtype, BCT was also not a factor associated with risk for recurrence. Conclusions and Relevance: The findings from this cohort study of patients with BRCA1 or BRCA2 pathogenic variants suggested that there were no significant differences in oncologic outcomes between patients who underwent BCT and those who underwent mastectomy. Therefore, breast conservation with close surveillance can be considered a viable treatment option for BRCA1 or BRCA2 pathogenic variant carriers. Further studies incorporating prospectively collected data are warranted to validate our findings.