To determine the risk of local-regional failure following post-mastectomy radiotherapy and the incidence of complications associated with such treatment.

We retrospectively analyzed the results in 309 patients with Stage I-III invasive breast cancer treated with post-mastectomy radiation therapy between 1975 and 1985. The median radiotherapy dose was 45 Gy in 1.8 to 2.25 Gy fractions. One hundred forty-seven (48%) of the patients received adjuvant systemic chemotherapy with 115 (78%) of these receiving a CMF-based or doxorubicin-containing regimen. The median follow-up time of surviving patients was 130 months (range, 28 to 191 months) after mastectomy.

Seventeen patients (6%) developed a local-regional failure at an interval of 4 to 87 months after radiotherapy. Moderate or severe complications related to radiotherapy and requiring treatment were uncommon. Symptomatic radiation pneumonitis occurred in four patients (1.3%), arm edema in 18 (5.8%), and brachial plexopathy in 2 (0.6%).

We conclude that post-operative radiotherapy is a safe and effective means of reducing local-regional failure following mastectomy. The efficacy of post-mastectomy radiotherapy in improving survival should be addressed in new large randomized controlled studies.