ABSTRACT
Radiotherapy involves the application of high-energy radiation to targeted areas of the body with the intention of killing tumor cells. The staging of cancers is a means by which practitioners classify tumors according to how advanced they are at the time of diagnosis. It is important to understand that the stage assigned to a cancer is set at the time of diagnosis and does not change with time. Staging information is used to plan treatment, predict outcome, monitor progress, and communicate. Radiation treatment involves the exposure of cancerous and surrounding tissue to high-energy x-rays or gamma rays, which damage the deoxyribose nucleic acid (DNA) of cells either directly or indirectly. Cells with DNA damaged beyond a certain point are unable to fulfill their normal function or divide. For patients with early-stage breast cancer, a mastectomy, which involves removal of all breast tissue, is an option for treatment.