To evaluate the outcomes for patients with Stage II breast cancer and one to three positive lymph nodes after mastectomy who were treated with observation or adjuvant radiotherapy to the chest wall (CW) with or without the regional lymphatics.

We retrospectively analyzed 238 patients with Stage II breast cancer (one to three positive lymph nodes) treated with mastectomy at the Massachusetts General Hospital between 1990 and 2004. The estimates of locoregional recurrence (LRR), disease-free survival (DFS), and overall survival were analyzed according to the delivery of radiotherapy and multiple prognostic factors.

LRR and DFS were significantly improved by postmastectomy radiotherapy (PMRT), with a 5- and 10-year LRR rate without PMRT of 6% and 11%, respectively and, with PMRT, of 0% at both 5 and 10 years (p = .02). The 5- and 10-year DFS rate without PMRT was 85% and 75%, respectively, and, with PMRT, was 93% at both 5 and 10 years (p = .03). A similar benefit was found for patients treated with RT to the CW alone. The LRR, DFS, and overall survival rate for patients treated to the CW only was 0%, 96%, and 95% at 10 years, respectively.

Our data suggest that adjuvant PMRT to the CW alone provides excellent disease control for patients with breast cancer <5 cm with one to three positive lymph nodes.