Can the addition of regional radiotherapy counterbalance important risk factors in breast cancer patients with extracapsular invasion of axillary lymph-node metastases?

Purpose: To evaluate if locoregional radiotherapy (RT) versus local irradiation only can alter the pattern of failure in breast cancer patients with extranodal invasion. Patients and Methods: From 08/1988 to 06/1998, 81 patients with extranodal invasion were treated with adjuvant RT (median total dose: 50.4 Gy), 46/81 only locally, 35/81 locoregionally due to presumed adverse parameters. The mean number of resected (positive) lymph nodes was 17 (seven). 78 patients received adjuvant systemic treatment(s). Results: Patients treated with locoregional RT had significantly more often lymphatic vessel invasion (LVI; 63% vs. 28%; p 0.003), T3/T4 tumors (43% vs. 17%; p = 0.014), and four or more positive lymph nodes (91% vs. 46%; p < 0.001) than patients irradiated only locally. Disease progression occurred in 24/81 patients (locoregional RT: 26% vs. local RT: 33%). The above risk factors were highly significant of worse outcome. Despite their overrepresentation in the locoregional RT group, no difference was found between both groups in regard to disease-free survival (DFS; p = 0.83) and overall survival (OS; p = 0.56), suggesting that regional RT was able to counterbalance the increased risk. There was even a trend toward a better 3-year DFS, 61% in locoregional RT and 37% in local RT, in the subgroup of patients with four or more positive lymph nodes. In a Cox regression model, higher T-stage, four or more positive lymph nodes, and LVI remained significant. For DFS and distant metastasis-free survival (DMFS), the absence of estrogen receptors and the omission of regional RT were also significant. Conclusion: Our data suggest that the addition of regional RT might be beneficial in selected subgroups of patients with extranodal invasion and other poor prognostic factors.