Clinical and molecular characterization of BRCA -associated breast cancer: results from the DBCG.

Background: In breast cancer (BC) patients a cancer predisposing BRCA1/2 mutation is associated with adverse tumor characteristics, risk assessment and treatment allocation. We aimed to estimate overall- (OS) and disease-free survival (DFS) according to tumor characteristics and treatment among women who within two years of definitive surgery for primary BC were shown to carry a mutation in BRCA1/2. Material and methods: From the clinical database of the Danish Breast Cancer Group we included 141 BRCA1 and 96 BRCA2 BC patients. Estrogen receptor and HER2 status were centrally reviewed on paraffin-embedded tumor tissue. Information on risk reducing surgery was obtained from the Danish Pathology and Patient Registries and included as time-dependent variables in Cox proportional hazard models. Results: Ten-year OS and DFS for BRCA1 BC patients were 78% (95% CI 69–85) and 74% (95% CI 64–81). Ten-year OS and DFS for BRCA2 BC were 88% (95% CI 78–94) and 84% (95% CI 74–91). BRCA1 BC patients as compared to BRCA2 BC patients had a higher risk of BC relapse or non-breast cancer within ten years of follow-up, independent of ER status (adjusted HR 2.78 95% CI 1.28–6.05, p=.01), but BRCA mutation was not associated with OS (adjusted HR 1.98, 95% CI 0.87–4.52, p=.10). In multivariate analysis, including both BRCA1 and BRCA2 carriers, no chemotherapy was associated with a higher risk of death (adjusted OS HR 3.58, 95% CI 1.29–9.97, p=.01) and risk reducing contralateral mastectomy (RRCM) was associated with a significantly reduced risk of death (adjusted OS HR 0.42, 95% CI =0.21–0.84, p=.01). Conclusion: Difference in OS between BRCA1 and BRCA2 BC patients could be ascribed to tumor-biology. BRCA1 BC patients may have a shorter ten-year DFS than BRCA2 BC patients. Chemotherapy and risk reducing contralateral mastectomy reduce mortality for both BRCA1 and BRCA2 BC patients. [ABSTRACT FROM AUTHOR]