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

Abstract

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.

Acknowledgments

We would like to thank Lejla Majdanac for her excellent assistance in collecting historical data from Rigshospitalet, Copenhagen University Hospital.

Disclosure statement

AMG participated in an advisory board meeting about BRCA testing in ovarian cancers in February 2016, funded by AstraZeneca.

Additional information

Funding

The study was supported financially by Region Zealand, Region of Southern Denmark, The Danish Cancer Research Foundation, Møbelarkitekt Aksel Clausens Foundation, Landsforeningen mod Brystkraeft, Karen A. Tolstrups Foundation and Axel Muusfeldts Foundation.