OUTLINE: This is a randomized, double-blind, placebo-controlled study. Patients are stratified according to radiation field (breast [post-lumpectomy] vs chest wall [post-mastectomy]), regional lymph nodes (treated vs not treated), and planned total radiation dose (including boost) (50-55 Gy vs > 55 Gy). Patients are randomized to 1 of 2 treatment arms.