RADIOBIOLOGICAL ASPECTS IN BRACHYTHERAPY OF SECONDARY METASTATIC VAGINAL CANCER
The search for optimal models of contact radiation therapy for the purpose of increasing the effectiveness of chemoradiotherapy for secondary vaginal cancer (metastatic forms) continues to be the subject of extensive discussion. Materials and methods. The National Cancer Institute, Department of Radiation Oncology conducted complex conservative treatment of 92 patients with metastatic cancer of the vagina II-III stages, T2-3 N0-1 M0 at the age of 28 to 72 years. Depending on the method of HDR (high dose rate - of higher than 12 Gy / h) brachytherapy, 3 groups were formed on the background of chemosensitizing agents (oral fluoropyrimidines, platinum preparations): 2 studies (28 patients who underwent HDR brachytherapy using 192Ir source and 30 patients with 60Co HDR source) and 34 patients of the control group, Which brachytherapy was carried out by 60Co sources with an average medium dose rate (MDR - from 2 Gy / h to 12 Gy / h). The total focal dose from combined radiotherapy was up to 80-90 Gy on the tumor focus and 44-46 Gy on the regions of regional metastasis. Brachytherapy was performed in the 5 Gy regimen 2 times a week. Results. Analysis of the direct results of the effectiveness of the use of 60Co or 192Ir sources with HDR brachytherapy and dynamic observation data for 3 months showed that the positive tumor response (complete + partial regression) in patients with metastatic vaginal cancer after the course of chemoradiotherapy increased by 20,1 % and 16,6 % application of 60Со МDR at brachytherapy. Toxic effects of treatment by the number and extent of their manifestations in the study groups of patients did not differ from the control group and did not exceed the second degree. Conclusions. Technologies of high-energy modern brachytherapy with high-dose rate sources of 192Ir and 60Co allow one to concentrate in a short time interval high doses of energy of ionizing radiation in a limited volume of tissues with minimal risks of severe radiation reactions or damage. The clinical effect of chemoradiotherapy is delayed. The use of radio modifiers in the process of combined radiotherapy in patients with metastatic vaginal cancer does not lead to toxic complications that adversely affect the quality of life of patients.