Introduction. Indications for radiation therapy after mastectomies with/without reconstruction at T12N01M0 remain unclear; treatment standards contain references to the possible administration of radiation therapy for factors that increase breast cancer recurrence. Materials and methods. A retrospective singlecenter, nonrandomized study enrolled 984 breast cancer patients treated at P.A. Gertsen Moscow Cancer Research Institute from 2014 to 2022. Patients were divided into 2 groups: a radiotherapy group and a nonradiotherapy group. Results and discussion. The paper presents an analysis of patients’ age, the histological structure of the tumor, immunohistochemical characteristics, tumor grade, multicentricity, presence of lymphovascular invasion, tumor cells, the state of R1 and R0 margins, and the tumor stage at risk of recurrence. Overall survival in the recurrence group accounted for 95.1%, in the nonrecurrence group – 98.4%. In the radiotherapy group (group I), the overall survival comprised 98.4%; metastases were diagnosed in 4.9% of cases. In thenonradiotherapy group (group II), the overall survival amounted to 98.2%; metastases were revealed in 5.9% of cases. Conclusion. Univariate analysis in the study groups showed that radiation therapy reduced the risk of relapse by 3.5%. In case of positive R1 margin, radiotherapy is recommended, which was confirmed in our study, the difference accounted for 14.5%, and in the presence of R1, radiotherapy is claimed to be necessary in the postoperative period. When analyzing the stage of breast cancer and the risk of recurrence, the statistical difference was revealed only at stage IIA (T1N1M0); radiation therapy reduced the risk of breast cancer recurrence. The statistical difference in groups I and II was detected at Grade 2 tumor, Ki67 level less than 50%, presence of tumor embolism and age of patients under 40 years. Radiation therapy after subcutaneous/skinsparing mastectomy reduces the recurrence risk by 3.2%; however, the overall survival in group I and group II accounted for 98.4 and 98.2%, respectively; the difference is not statistically significant. In our study, the criteria for prescribing radiation therapy in the postoperative period include: young age of the patients, R1 resection margin, luminal/nonluminal HER2 positive type, cN1, presence of tumor embolism.
