Modern radiotherapy of breast cancer is carried out on megavoltage devices-linear accelerators, which enables the achievement of optimal precision and homogeneous irradiation of the target volume with maximum sparing of the surrounding healthy structures, primarily the heart and lungs. Radiotherapy is applied after breast cancer surgery, and for locally advanced tumors, radiotherapy is applied in combination with surgery and systemic therapy (chemotherapy, hormone therapy). The initial therapy for locally advanced breast cancer is chemotherapy, while radiotherapy can be carried out in the case of a positive response to non-adjuvant (preoperative) chemotherapy and mastectomy, or in the absence of response to chemotherapy and tumor inoperability as preoperative or radical radiotherapy.

     The goal of postoperative radiotherapy is to achieve a better local effect and prolong the survival time without recurrence of the disease. After a radical mastectomy, in high-risk patients radiation therapy of the chest wall and regional lymphatic structures is carried out, and depending on the pathohistological findings of the material, the breast and lymph nodes in the armpit are removed.

     Postoperative radiotherapy, after sparing surgery, reduces the occurrence of local tumor recurrence. The result of the initial treatment of ductal carcinoma in situ with a conservative surgical approach and postoperative radiotherapy gives high percentages of overall survival time, as well as survival time without disease recurrence. Five-year survival 98–100 %. The risk of local tumor recurrence is 0-4% in 5 years.

     Postoperative radiotherapy after sparing surgery for invasive breast cancer involves radiation therapy of the remaining breast tissue, which is always carried out, while regional lymph nodes are irradiated only in special cases when there is an increased risk of relapse-reoccurrence of the disease.

     The breast is irradiated with a dose of 50 Gy in 25 fractions (5 weeks). In addition, in certain cases, a boost is added – an additional dose to the tumor bed with a TD of 10-16 Gy in 5-8 fractions. An additional dose is recommended for patients under the age of 50 and with a high (III) tumor grade, as well as for patients over the age of 50 who have an increased risk of local recurrence of the disease.

     It is recommended that radiotherapy will be applied within 8 weeks of the surgery.