Stereotactic Radiation Therapy for HE2-positive Oligometastatic Breast Cancer

This study involves two non-randomized groups of patients: the observation group and the comparison group. The comparison group will retrospectively include data on 29 patients with oligometastatic HER2-positive breast cancer who were treated with trastuzumab-emtansine and had a history of SRT. The dynamics of the process will be evaluated retrospectively using CT and MRI data according to RECIST 1.1 criteria. The main statistical indicators will be calculated based on the patients' medical documentation. The prospective part of this study aims to include 29 patients with oligometastatic HER2-positive breast cancer. These patients will undergo SRT for up to 2 cycles, depending on the location of the irradiated focus, followed by administration of trastuzumab emtansine 3.6 mcg/kg once every 3 weeks, up to 4 total cycles. Trastuzumab emtansine therapy will be initiated 24 hours after the end of the course of SRT. Tumor foci will be assessed according to RECIST 1.1 criteria. Objective response, general condition, and adverse events will be evaluated before, during, and after treatment. Patients will be stratified by age, location of metastatic foci, and treatment. Outpatient patient records, medical histories, clinical and laboratory examination data, morphological examination data, CT findings, MRI findings will be used as sources of information for analyzing the results of diagnosis and treatment.