Post-mastectomy radiation therapy: translating local benefits into improved survival.

Several randomized trials and the most recent meta-analysis from the Oxford Overview have confirmed the efficacy of post-mastectomy radiation therapy (PMRT) in improving local control and long-term survival. The survival advantage of PMRT has been established in patients with a 10% risk of local regional recurrence. Patients with four or more positive lymph nodes fall in this category, even with effective systemic therapy. However, it remains difficult to identify the subset of patients with 1-3 positive lymph nodes at highest risk of local recurrence, who would most likely demonstrate a survival benefit with PMRT. When PMRT is used, careful treatment planning, particularly with regard to cardiac dose, is critical to minimizing serious late effects of treatment. Further developments in pathologic stratification of these patients, guided by expression profiles or novel biologic markers, are required to enable individualized assessment of long-term therapeutic risks and benefits.