Impact of BRCA1/2 pathogenic variants on ipsilateral breast tumor recurrence and prognosis following breast-conserving surgery.

The risk of ipsilateral breast tumor recurrence (IBTR) and the prognostic outcomes of breast-conserving surgery (BCS) for germline BRCA1/2 pathogenic variant carriers (BRCA+) remain controversial. This study aimed to investigate the differences in the incidence of IBTR and prognosis between BRCA + and noncarriers (BRCA-) after BCS. A retrospective chart review was performed in patients with stage 0-III breast cancer who underwent genetic testing for germline BRCA1/2 and BCS between 1996 and 2020. We compared the incidence of IBTR and the characteristics and prognostic outcomes of IBTR, including overall survival (OS), breast cancer-specific survival (BCSS), and distant recurrence-free survival (DRFS), between BRCA + and BRCA- after BCS. We analyzed 551 patients (587 breasts with cancer), including 61 carriers (64 breasts with cancer). During the median follow-up period of 5.3 years, the 5-year IBTR rates were 3.6% in the BRCA+ group and 5.1% in the BRCA- group, and the 10-year IBTR rates were 9.5% and 8.8%, respectively (p = 0.489). The median times to IBTR were 10.2 years in BRCA + and 3.5 years in BRCA-. The discordance rate of cancer subtypes between IBTR and primary cancer was significantly higher in BRCA+ than in BRCA- (p = 0.012). No significant differences were observed in the OS, BCSS, or DRFS between the two cohorts. No significant differences were observed in the IBTR risk or prognostic outcomes between BRCA + and BRCA- after BCS. However, the longer time to IBTR and the clinicopathological features potentially consistent with new primary cancers in BRCA+ suggest the importance of shared decision-making regarding BCS and long-term intensive breast surveillance after BCS in BRCA+.