First isolated locoregional recurrence following mastectomy for breast cancer: results of a phase III multicenter study comparing systemic treatment with observation after excision and radiation. Swiss Group for Clinical Cancer Research.

PURPOSE: We performed a randomized phase III multicenter study to compare systemic treatment versus no treatment after complete excision and radiotherapy for isolated first locoregional recurrence in patients with breast cancer. PATIENTS AND METHODS: One hundred sixty-seven good-risk patients with an estrogen receptor (ER+) positive recurrence or, in case of unknown receptor status, a disease-free interval (DFI) of greater than 12 months and < or = three recurrent tumor nodules each < or = 3 cm in diameter were entered onto the study. They were randomized to observation subsequent to local treatment or to receive tamoxifen (TAM) until disease progression. Seventy-nine percent of the patients were postmenopausal. RESULTS: The median observation period for the entire study population was 6.3 years. The median disease-free survival (DFS) duration was 26 months for observation and 82 months for TAM patients (P = .007). This was mainly due to the reduction of further local recurrences, whereas the occurrence of early distant metastases was delayed. A multivariate analysis identified DFI and treatment with TAM as significant prognostic factors for DFS. The 5-year overall survival (OS) rates were 76% and 74%, respectively (P = .77). DFI was also a prognostic factor for OS. CONCLUSION: Systemic therapy with TAM after isolated locoregional recurrence of breast cancer significantly increased 5-year DFS rates from 36% to 59% compared with observation alone and prolonged median DFS by more than 4.5 years in patients with ER+ tumors or in the case of unknown ER status with a DFI of greater than 12 months and minimal tumor burden. Treatment with TAM currently has no significant impact on OS, but the median survival duration of the study population has not yet been reached.