To assess patterns of failure and how selected prognostic and treatment factors affect the risks of locoregional failure (LRF) after mastectomy in breast cancer patients with histologically involved axillary nodes treated with chemotherapy with or without tamoxifen without irradiation.

The study population consisted of 2,016 patients entered onto four randomized trials conducted by the Eastern Cooperative Oncology Group. The median follow-up time for patients without recurrence was 12.1 years (range, 0.07 to 19.1 years).

A total of 1,099 patients (55%) experienced disease recurrence. The first sites of failure were as follows: isolated LRF, 254 (13%); LRF with simultaneous distant failure (DF), 166 (8%); and distant only, 679 (34%). The risk of LRF with or without simultaneous DF at 10 years was 12.9% in patients with one to three positive nodes and 28.7% for patients with four or more positive nodes. Multivariate analysis showed that increasing tumor size, increasing numbers of involved nodes, negative estrogen receptor protein status, and decreasing number of nodes examined were significant for increasing the rate of LRF with or without simultaneous DF.

LRF after mastectomy is a substantial clinical problem, despite the use of chemotherapy with or without tamoxifen. Prospective randomized trials will be necessary to estimate accurately the potential disease-free and overall survival benefits of postmastectomy radiotherapy for patients in particular prognostic subgroups treated with presently used and future systemic therapy regimens.