Is avoiding post-mastectomy radiotherapy justified for patients with four or more involved axillary nodes and endocrine-responsive tumours? Lessons from a series in a single institution

Background: Current guidelines for post-mastectomy radiotherapy (PMRT) derive largely from extrapolating information from multicentre trials. The aim of this study was to describe outcomes of patients who underwent mastectomy without radiotherapy in a single institution. Patients and methods: 650 patients had total mastectomy and axillary dissection without PMRT between 1997 and 2001. Median follow-up was 65 months. Results: 5-year cumulative incidence of loco-regional recurrence (LRR) was 6.8% (3.0, 8.1, 9.9% in node negative, 1-3, >= 4 positive nodes, respectively). At the multivariate analysis, positive lymph nodes and endocrine non-responsive tumours were found to shorten LRR disease-free survival. In patients with positive hormone receptors, 5-year cumulative incidence of LRR disease-free survival were 2.3%, 7.6% and 7.6% for node negative, 1-3 and >= 4 positive lymph nodes, respectively. The same figures were 5.9%, 10.3% and 20.0% in patients with endocrine non-responsive turnours. Conclusions: patients with enclocrine- responsive tumours treated by mastectomy and complete (level 111) axillary dissection have a low risk of LRR even if four or more positive lymph nodes are involved, thus giving rise to doubts on the use of PMRT in this subset of patients. On the other hand, PMRT might play a role for patients with negative hormone receptors and four or more positive nodes.