Postmastectomy Chest Wall Radiation with Electron-Beam Therapy

Abstract

Postmastectomy chest wall radiation therapy using electron-beam therapy has been reported to increase lung radiation dose and the potential for pneumonitis. These reports describe treatment with varying energy electron beams prescribed to the breast/chest wall junction. Because the tissue at risk includes dermal lymphatics and subcutaneous tissues, low-energy electron beams may reduce lung radiation dose and the incidence of pneumonitis yet preserve good local control. At the University of Louisville, patients who have undergone mastectomy are treated with 6-MeV electron beam and bolus. From 1985 through 1998, 273 patients underwent postmastectomy radiation therapy at the University of Louisville. The chest wall was treated using 6-MeV electron beam with 5-mm bolus prescribed to the 90% isodose-line, ensuring adequate dermal lymphatic dose. Internal mammary nodes were treated with electron-beam energy sufficient to treat to depth (approximately 15 MeV). Supraclavicular nodes were treated using 6-MV photon beam. Patients' charts were reviewed with respect to complications and outcome. Radiation pneumonitis was confirmed in one case (0.4%). The pneumonitis resolved with prednisone treatment. Twenty patients experienced locoregional failure (7.3%), 14 of whom failed in the chest wall (5.1%). Local control in our study is excellent and comparable to results expected for postmastectomy radiation therapy as reported in the literature. We conclude that postmastectomy patients can be treated with low-energy electron beam radiation therapy, protecting underlying lung without sacrificing local disease control.