In radiation therapy, high-energy rays are used to destroy cancer cells by injuring their ability to multiply. Radiation therapy is usually given after a lumpectomy to sterilize any cancer cells that might be left in the breast.

In standard therapy, a machine delivers radiation to the breast and in some cases to the lymph nodes in the armpit. The usual schedule for radiation therapy is 5 days a week for 5 to 6 weeks. Each radiation treatment takes only about 2 to 5 minutes.
During treatment planning, your chest area will be marked with ink or with a few long-lasting tattoos. These marks need to stay on your skin during the entire treatment period. They mark where the radiation is aimed.

Radiation treatment is not painful. Some women experience tingling or warmth in the treated area. Others report feeling more tired than usual and decrease their activity during the weeks of daily treatments. Side effects may include feeling more tired than usual and skin irritations, such as itchiness, redness, soreness, peeling, darkening, or shininess of the breast. Radiation to the breast DOES NOT cause hair loss, vomiting, or diarrhea. Long-term changes may include changes in the shape and color of the treated breast, spider veins and heaviness of the breast.