Background
Retrospective multicenter cohort, N=4009 (576 with BRCA1/2 mutations), invasive breast cancer (pT1-3, N0-3), all underwent BRCA testing 2008-2018, median follow-up 93 months. Analyzed contralateral breast cancer (CBC) risk factors and pathologic predictors by BRCA genotype to inform risk-reducing surgery discussions.
Interventions and follow up
Arm A: BRCA1 carriers (analyzed for pathologic CBC predictors)
Arm B: BRCA2 carriers (analyzed for pathologic CBC predictors)
Primary endpoint: Contralateral breast cancer (CBC) incidence
mFollow up: Median 93 months
Arm B: BRCA2 carriers (analyzed for pathologic CBC predictors)
Primary endpoint: Contralateral breast cancer (CBC) incidence
mFollow up: Median 93 months
Results
CBC incidence: 278 cases (6.9% overall); no significant difference between BRCA1 vs BRCA2 (P=.07)
BRCA1 (age <50): triple-negative subtype strongly associated with CBC risk (correspondence analysis r=0.93)
BRCA2 (all ages): high Ki-67 (≥20%) prominently associated with CBC (r=0.93)
BRCA1 (age <50): triple-negative subtype strongly associated with CBC risk (correspondence analysis r=0.93)
BRCA2 (all ages): high Ki-67 (≥20%) prominently associated with CBC (r=0.93)
Adverse events
Surgical: complications of risk-reducing prophylactic mastectomy (not detailed in this outcomes analysis)
Psychosocial: psychological impact and body-image changes recognized harms of prophylactic mastectomy; rates NR
Psychosocial: psychological impact and body-image changes recognized harms of prophylactic mastectomy; rates NR
Conclusions
Although no difference in overall CBC risk between BRCA1 and BRCA2 carriers, correspondence analysis revealed distinct pathologic predictors. Young BRCA1 carriers with triple-negative/high-grade tumors and BRCA2 carriers with high Ki-67 may benefit from a risk-reducing prophylactic mastectomy discussion.
Key Limitations
Retrospective design; selection bias in BRCA testing; heterogeneous prophylactic mastectomy uptake not reported; correspondence analysis exploratory (post hoc); no data on actual risk-reducing mastectomy outcomes or patient preferences; limited germline vs somatic comparison.
Clinical Context
Identifies pathologic subtypes in BRCA carriers at highest CBC risk, informing counseling for risk-reducing strategies. ASCO and ESMO guidance supports discussing bilateral risk-reducing mastectomy in BRCA carriers diagnosed with breast cancer, individualized to age and tumor biology. This study suggests younger BRCA1 carriers with TNBC and high-Ki-67 BRCA2 carriers as priority candidates for that discussion. ESMO-MCBS: not applicable (retrospective risk-factor analysis).