Breast cancer is the most common female malignancy. Survival rate varies throughout the world, but it remains the third most common cause of death in women. Etiology of breast cancer is mostly unknown, but there are several known risk factors which are associated with its development, such as elder age and hereditary appearance. Mammography is a diagnostic procedure widely used as a part of preventive program with purpose of finding the breast cancer in early phase of disease, when it can still be curable. To make a decision about treatment modality is obligated to have a pathology report containing the data about tumor biology, and stage of disease. Treatment decision must be made by multidisciplinary team and treatment options involves surgery, radiotherapy, chemotherapy, hormonal therapy, therapy with small molecules, supportive therapy and combination of all. Radiotherapy is a type of treatment in which ionizing radiation is used to achieve therapeutic effect. It can be implemented as teleradiotherapy and brachytherapy. Radiotherapy can either be radical or palliative. Radical radiotherapy is adjuvant, and is performed after the surgical procedure. If chemotherapy and hormone therapy are indicated, radiotherapy is performed after the completion of chemotherapy, while hormone therapy can be performed concomitant with radiotherapy. After breast conserving surgery, radiation is preformed over whole breast tissue. After complete mastectomy radiation is preformed over the chest wall. In the case of lymph nodes metastasis radiotherapy of regional lymph nodes needs to be performed. Postoperative radiotherapy along with chemotherapy reduces the risk of loco regional recurrence of the disease and prolongs overall survival in a breast cancer patient.