Prophylactic Irradiation to the Contralateral Breast for BRCA Mutation Carriers Undergoing Treatment for Breast Cancer

Overview

Women with BRCA germline mutations face a very high risk of developing breast cancer during their lives. It was shown that for carrier patients, breast conservation, comprising of lumpectomy followed by whole breast radiation, was not associated with increased risk of ipsilateral breast cancer recurrence as compared with non carriers (10-15% over 10 years), especially if they also underwent prophylactic oophorectomy. Yet their risk of subsequent contralateral breast cancer was significantly increased, reported as high as 25-30% over 10 years and 40% over 15 years, as compared to 3% and 7% respectively in non carriers. The reduction in ipsilateral disease was attributed to radiation of the affected breast. We propose that for breast cancer patients with BRCA germline mutation that choose to have breast-conserving therapy and refuse prophylactic contralateral mastectomy, prophylactic radiation to the contralateral breast may reduce the rate of subsequent contralateral breast cancer and offer an option for risk reduction.

Trial design and statistics: This is a multi center- phase II open comparative trial. "Patients" - Those who choose prophylactic contralateral breast irradiation. "Controls" - Those that do not opt for prophylactic irradiation or mastectomy. Objective - to compare the rate of contralateral breast cancer in "patients" versus "controls". Assuming that 2/3 of the eligible carrier breast cancer patients refuse the procedure: To detect a difference of 10% vs. 25% in the incidence of contralateral breast cancer with power = 80%, alpha = 0.05, 80 patients and 160 controls need to be enrolled. Treatment: Chemotherapy, Hormonal therapy and XRT to the affected breast as per treating institution. Radiation therapy: Patients will undergo a pre-treatment planning CT with 5mm cuts in the treatment position, on a breast board, with both arms extended above their head. The organs at risk (heart, lungs) will be contoured on the CT scan. The affected breast (with the index lesion) and associated lymphatic drainage will be treated according to the treating physician decision. The contralateral breast will be treated with 2 tangent fields, using 1.8-2 Gy/fx to a total dose of 50-50.4 Gy. The whole breast will be treated according to traditional guidelines and as described in the RTOG/NSABP B39 study. The heart should be completely blocked for left sided breasts, included lung tissue should be reduced to minimum. No overlapping field is allowed on the skin between the two breast fields in the midline. Maximal dose should not exceed 110%. Follow up: The treating physician will follow the patient every 2 weeks during the radiation treatment. Side effects will be scored and recorded in the patients chart according to the Common Terminology Criteria for Adverse Events v3.0. Subsequent follow-up schedule according to the treating institution and ASCO guidelines. Patients will undergo annual mammogram and breasts US. Annual breasts MRI and bilateral salpingo-oophorectomy will be recommended. Ipsilateral and contralateral breast cancer will be recorded and reported. Any subsequent malignancy other than breast cancer will be reported. Long-term radiation side effects will be recorded.