CONTEMPORARY APPROACHES TO PROGNOSTICATION AND MANAGEMENT OF PELVIC RADIATION INJURIES IN GYNECOLOGICAL CANCER PATIENTS

Background. Rapid development of radiotherapeutic techniques and implementation of radiation therapy (RT) nanotechnologies in practice, taking into account principles of radiobiology, ensures that the planned dose will be delivered to the target volume with minimal irradiation of healthy tissues while maintaining the guaranteed RT quality. Therefore, further advance of RT involves not only implementation of the new technologies in radiation practice, but also the intensive developments in fields of radiation medicine and clinical radiobiology. Objective: search for optimal models of the high-energy (HDR – high dose rate) brachytherapy (BT) using the 192Ir source in comparison with effects of the reference gamma radiation from 60Co, thereby, to increase the effectiveness of chemoradiation therapy (CRT) of gynecological cancer patients (GCPs) with minimal radiation loads on critical organs and tissues in the tumor environment. The radiobiological study was aimed to determine the feasibility of using the transmembrane potential (TMP) and intensity of reactive oxygen species (ROS) production in peripheral blood lymphocytes (PBL) as predictors of radiosensitivity of non-malignant cells from the tumor environment or its bed in order to minimize the RT complications in GCPs. Materials and methods. Patients (n = 115) with cancer stages II–III, T2–3N0–1M0 were managed with comprehensive conservative treatment. Three groups of patients were selected depending on the applied HDR BT method against a background of the administered chemosensitizing agents. Blood samples of GCPs (n = 24) before the RT initiation and of apparently healthy individuals (AHIs, i.e. the control group, n = 18) were taken for the radiobiological research. Results. Review of the direct results of 60Co or 192Ir sources use in HDR BT and of the follow-up data showed the increased tumor positive response in the main study groups after CRT course by respectively 16.6 % and 20.1 % in comparison with 60Со HDR BT administration. Concerning local reactions it was noted that grade II radiation reactions were almost absent in the main groups. According to the results of radiobiological studies, it was established that TMP level in PBL of GCPs was 1.36 times higher than in AHIs. Conclusions. Thus, the emerging of late radiation injuries depended on the accuracy of of individual computer planning and correct reproduction of the planned RT course, timely correction of treatment programs, use of a complex of rational medical prophylaxis, severity of tumor process and concomitant disorders, as well as on the used type of HDR radiation sources (192Ir and 60Co). Changes in TMP values and intensity of ROS production in PBL of GCPs in comparison with AHIs, and the high values of these parameters in PBL of individual patients are a rationale to specify them as additional indicators characterizing the possibility of radiation complications before the RT planning. Key words: HDR brachytherapy, 192Ir and 60Co high dose-rate sources.