Effects of brachytherapy on cytogenetic parameters and oxidative status in peripheral blood lymphocytes of gynecologic cancer patients.

BACKGROUND: The state-of-the-art brachytherapy technologies with high-dose sources of 60Co and 192Ir within contemporary treatment protocols for cancer patients allow achieving maximum dose distribution in the clinical target and with minimum radiation exposure of surrounding organs and tissues. For minimization and overcoming the early and late radiation complications, development of respective radiobiological criteria along with perfecting of physical and technical characteristics of the ionizing radiation sources are required. AIM: To study the effect of 192Ir radiation on the chromosomal aberrations and prooxidant/antioxidant status of blood lymphocytes in gynecological cancer patients. MATERIALS AND METHODS: The patients (n = 45) with endometrial, cervical and secondary cancer of vagina were enrolled in the study. For brachytherapy, the irradiation of vaginal mucosa was conducted using "GammaMed plus" device for contact radiation therapy with 192Ir source. Prior to irradiation and in 20-24 h after brachytherapy session, the venous blood samples were obtained and peripheral blood lymphocytes (PBL) were cultured for cytogenetic analysis. The prooxidant/antioxidant status was determined in hemolysates by the method of hydrogen peroxide-induced chemiluminescence. RESULTS: The average level of spontaneous chromosome aberrations in PBL of the patients was (7.8 ± 0.4) per 100 metaphases, which is more than twice higher than the upper limit of the average population values. The frequency of chromosome aberrations in PBL of patients after brachytherapy session was (15.3 ± 1.0) per 100 metaphases. An increased intensity of O2- generation by PBL after brachytherapy session was also noticed. CONCLUSION: Local irradiation at a dose of 6 Gy featuring the first dose fraction of brachytherapy induces extra chromosomal aberrations in PBL of gynecological cancer patients and intensifies prooxidant processes in the blood.

IRIDIUM-192 RADIOTHERAPY BENEFITS IN THE MANAGEMENT OF GYNECOLOGICAL TUMORS. / PEREVAGY IONIZUIuChOGO VYPROMINIuVANNIa IRYDIIu-192 U PROMENEVOMU LIKUVANNI ONKOGINEKOLOGIChNYKh ZAKhVORIuVAN'.

BACKGROUND: Application of the most advanced radiation technologies of brachytherapy featuring the high dose ratesources i.e. 60Co and 192Ir within contemporary management protocols for gynecological cancer provides maximum dosedistribution in the clinical target along with minimal radiation exposure on surrounding organs and tissues. It involvesirradiation of large spaces with delivery of high therapeutic doses at the tolerance bound of «critical¼ organs (bladder,rectum) and tissues. Thus minimization of the early and late radiation complications, life span extent and quality oflife increase remain just the issues in contemporary radiation oncology requiring therefore the elaboration of radiobiological criteria along with substantiation of physiсо-engineering properties of the radiation sources. Taking intoaccount the basic radiobiological patterns will ensure a definitive further progress in the field of radiation oncology. OBJECTIVE: to study and compare the biological effects of 192Ir with the effects of the reference gamma radiation 60Coand increase the effectiveness of brachytherapy using a 192Ir source. MATERIALS AND METHODS: Radiobiological dosimetry on the basis of a test system of peripheral blood lymphocytesfrom the gynecological cancer patients with subsequent cytogenetic analysis of radiation-induced chromosomeaberrations was performed to study and compare the biological effects of 192Ir and reference 60Со γ-radiation, and toenhance the efficiency of 192Ir brachytherapy. RESULTS: Radiation markers, i.e. dicentric chromosomes with an accompanying paired fragment prevailed in thespectrum of radiation-induced damage. Variability of individual cytogenetic parameters of peripheral lymphocytesupon the first fraction of irradiation at the same dose of 5 Gy indicated an individual sensitivity of patients to the192Ir γ-irradiation. Comprehensive conservative treatment with adjuvant radiotherapy was applied to the patients(n = 98) having got secondary vaginal cancer stage II-III, T2-3N0-1M0. The high dose-rate (HDR) brachytherapy using 192Ir radiation sources was applied in the main study group (n = 37), HDR brachytherapy using 60Co radiation sourceswas applied in the control group (n = 35). CONCLUSION: The HDR brachytherapy with 192Ir and 60Co sources on the up-to-date technology intensive devices provides a high accuracy of dose distributions when irradiating the malignant neoplasms with minimized radiationexposure to the «critical¼ tissues. Treatment results are improved therefore. The use of 192Ir radiation sources compared with 60Co ones resulted in an increased throughput of treatment, enhanced tumor regression, and reduced incidence of radiation effects on the critical organs. Currently we perform the radiobiological studies on somatic cellsfrom cancer patients at the genetic, biochemical, biophysical, and cytological levels in order to receive a biologicalindication of radiation damage under the impact of 192Ir isotope. Continuation of clinical trials with radiobiologicalsupport will provide an opportunity to predict the early and late radiation complications and thus to provide a personalized approach in brachytherapy of cancer patients using the 192Ir sources of γ-rays.