Efficacy of Breast Conservation Therapy in Early Stage Bilateral Breast Cancer

The purpose of this study was to evaluate the outcome of patients with bilateral breast cancer as compared to unilateral breast cancer treated with breast conservation therapy. Sixty patients with bilateral breast cancer (BBC) and 1,080 unilateral breast cancer (UBC) patients treated with breast conservation therapy from 1977 to 1994 were analyzed for outcome. Of the 60 bilateral patients, 44 were metachronous bilateral breast cancer patients (MBBC) and 16 were synchronous bilateral breast cancer patients (SBBC). The majority of patients received lumpectomy, axillary node dissection, and localized radiation therapy. Median tumor size was 1.4 cm for BBC and 1.5 cm for UBC patients. Median total dose to the tumor bed was 60 Gy for both unilateral and bilateral patients. Of the 44 MBBC patients, 14 received breast conservation for both the first and second lesions, while 30 received breast conservation for only the second metachronous lesion. Thus 58 lesions in 44 patients were treated with breast conservation therapy. Of the SBBC patients, 13 of 16 patients received breast-conserving therapy for both breasts, while 3 received a mastectomy for the second synchronous primary. Median follow-up was 50 months for SBBC patients, 45 months for MBBC patients, and 52 months for UBC patients. Local control and survival were analyzed in patients with SBBC, MBBC, and UBC. The interval to development of local recurrence and survival were calculated from the time of development of the second breast lesion in patients with MBBC. No differences were found for survival and failure-free survival in patients with SBBC, MBBC, or UBC. Five-year overall survival by lifetable analysis was 76% for SBBC, 78% for MBBC, and 87% for UBC patients (p = 0.32 by log-rank analysis). The 5-year failure-free survival was 79% for SBBC, 73% for MBBC, and 85% for UBC patients (p = 0.28 by log-rank analysis). No significant differences were seen for median age, tumor size, pathologic node status, tamoxifen use, chemotherapy use, or median total radiation dose for SBBC, MBBC, or UBC patients. A significant difference was found in the incidence of family history of breast cancer in patients with unilateral versus bilateral breast cancer (p = 0.028 by chi-square analysis). However, there was no difference in outcome of patients by family history of breast cancer. The local control was identical in both BBC and UBC patients, with a local failure rate of 3%. Therefore, breast conservation therapy in local-regional, early stage breast cancer is a rational and efficacious treatment modality for patients with SBBC, MBBC, and UBC.