It is most often used with breast conserving surgery, but may also be recommended after a mastectomy for women with four or more positive lymph nodes. The purpose is to destroy any cancer cells that may be left after breast surgery. It may also be used palliatively, e.g., relieve symptoms, to shrink tumors and reduce pressure, bleeding, pain, or other symptoms of advanced cancer.
Cancer cells grow and divide rapidly, and they are very sensitive to the effects of radiation.
Normal cells grow and divide less rapidly and recover more fully from the effects of radiation than cancer cells. The side effects experienced from radiation are the result of temporary damage to the normal cells. It is important to realize that the side effects from radiation are directly related to the dose and the area being treated. The degree of skin reaction is very individual. Skin irritation will continue for approximately 2 weeks following the end of treatment.