Risk of Breast Cancer Recurrence and Contralateral Breast Cancer in Relation to BRCA1 and BRCA2 Mutation Status Following Breast-conserving Surgery and Radiotherapy

BRCA1 and BRCA2 germline mutations are associated with a strong risk of breast cancer, which may preclude breast-conserving treatment in carriers. This study examined whether mutation status influenced the rate of breast cancer recurrence following breast-conserving treatment. BRCA1 and BRCA2 genes were screened for germline mutations in 131 patients with a family history of breast and/or ovarian cancer, who had been treated with breast-conserving surgery and radiotherapy. The 131 patients with familial history were matched to 261 patients without, according to age at diagnosis and year of treatment. The follow-up of controls was at least equal to the time-interval between diagnosis and genetic testing in familial cases. Matched cohorts were compared according to rates of breast cancer recurrence as first event and contralateral breast cancer using log-rank tests. BRCA1/2 mutations were found in 20.6% patients with a family history. Nineteen patients had a BRCA1 mutation and 8 had a BRCA2 mutation. Breast cancers in mutation carriers were more often grade III (p<10-4) and oestrogen receptor negative (p=0.005) than tumours in both non-carriers and controls. Median follow-up for all 392 patients was 8.75 years. No significant differences in breast cancer recurrence as first event were seen between BRCA1/2 tumours and controls (p=0.47), carriers and non-carriers with a family history (p=0.96), or non-carriers and controls (p=0.10). On multivariate analysis, age was the most important factor significantly predicting for breast cancer recurrence. The rate of contralateral breast cancer was significantly increased in all patients with a family history: BRCA1/2 carriers versus controls (p=0.0003), non-carriers versus controls (p=0.0034) and carriers versus non-carriers (p=0.02). At a 9-year median follow-up, the rate of ipsilateral breast cancer recurrence was not higher in BRCA1 and BRCA2 mutation carriers than in non-carriers with a family history or sporadic cases. These results support the hypothesis that breast tumours in BRCA carriers are more sensitive to radiation. Therefore, breast-conserving treatment can be offered to these patients. However, longer follow-up is needed to ensure that the rate of new primary cancer in the treated breast does not increase in the long-term.