Radiation therapy typically involves using a large machine called a linear accelerator to deliver precise amounts of high-energy radiation to kill cancer cells. The radiation stops the reproduction of cancer cells while minimizing damage to healthy tissues. Radiation therapy has been shown to improve survival in women with breast cancer.
Incidence and Mortality
Estimated new cases and deaths from breast cancer (men only) in the United States in 2013:
New cases: 2,240.
Male breast cancer is rare. Less than 1% of all breast carcinomas occur in men.[3,4] The mean age at diagnosis is between 60 and 70 years, though men of all ages can be affected with the disease.
Predisposing risk factors  appear to include radiation exposure, estrogen administration, and diseases associated with hyperestrogenism,...
Radiation therapy is painless. However, some women experience side effects, which can include:
Redness, discomfort, and dryness of the skin in the treated area. Your doctor will recommend a specific treatment if this happens. The redness can take as long as a year to fade.
Fatigue, usually starting two to three weeks after treatment begins. The fatigue increases during the duration of treatment and goes away about a month after treatment ends. Fatigue should not disable you. Most women cope by taking a nap or by going to bed earlier.
Reduced blood counts. Your blood will be checked regularly, especially if you are also receiving chemotherapy.
Sometimes women also experience a sore mouth or throat, or dry mouth, if these areas are irradiated.