Radiation therapy utilizes high-energy beams to destroy cancer cells. Radiation for breast cancer treatment can be given after lumpectomy or mastectomy depending on the circumstances. Radiation attacks the DNA structure of cancer cells which affects their ability to grow. Radiation does affect healthy cells; however, healthy cells are able to repair themselves. Radiation therapy following surgery improves the chances that cancer will not return in that area. Therefore, your doctor may recommend radiation therapy along with other breast cancer treatments.