Irradiation effect after mastectomy on breast cancer recurrence in patients presenting with locally advanced disease

BackgroundCurrent guidelines recommend postmastectomy irradiation (PMI) for patients with tumors >5 cm and/or ≥4 positive lymph nodes. This study evaluates the effect of PMI on recurrence and survival within tumor size and node status groups.MethodsLocoregional and distant recurrences and survival for different tumor and treatment characteristics were analyzed in 2,797 patients with invasive breast cancer treated with mastectomy.ResultsTumor size, positive nodes, extranodal extension, lymphatic/vascular invasion, estrogen receptor/progesterone negative, HER-2 positive, and high grade were associated with significantly increased recurrence. In patients with ≥4 positive nodes and patients with tumors >5 cm and positive nodes, PMI decreased local and distant recurrence (overall 53% vs 24%, P < .001) and increased disease-free survival (P < .001) but not overall survival. In patients with less disease, a benefit from PMI irradiation could not be identified.ConclusionsPMI is indicated for patients with ≥4 positive nodes or patients with tumors >5 cm and positive nodes.