Prediction of radiation complications by determining the blood oxidation processes in cervical cancer patients under chemoradiotherapy

Abstract

Background. Radiotherapy (RT) is one of the principal methods in cancer management, and its administration in oncology practice is much wider nowadays because of the increased incidence of newly diagnosed cancer cases with wide spread and aggressive course of tumor process, and also in view of organ-sparing strategies in the combined treatment. However, the radiation reactions, especially local ones in rectum or bladder, can’t be completely avoided even using the most advanced radiotherapy facilities and dosimetry planning. Therefore, at present time not only technical modernization, but also the progress in radiobiology should be considered. Given the cytotoxic properties of some anticancer drugs, they are used in the combined therapy of cervical cancer (CC) to receive a radiosensitizing effect on the malignant cells. In particular, cisplatin inhibits reparative processes by affecting the enzymes involved in restoring the integrity of DNA or chromosome structure. Administration of the combined radiation and chemotherapy leads not only to an increase in the percentage of tumor regression, but also to an increase in the number of radiation injuries to healthy tissues. Therefore, prediction of such injuries, research and development of means of their prevention and treatment in the regimen of chemoradiotherapy (ChRT) of CC is extremely urgent and remains an unsolved problem to date. Purpose. Development of personalized approaches in ChRT in CC patients by studying its efficiency, assessing its toxicity, and predicting radiation injuries according to the data of blood oxidative processes in patients. Materials and methods. The combined radiotherapy (CRT) and ChRT were administered to the stage IIB–IIIB CC (T2b-3bN0-1M0) patients (n = 105) at the National Cancer Institute. Patients aged 25–75 years were divided into two groups: the study group and the comparison group. Complex clinical examination was conducted prior to treatment featuring the assay of tumor parameters, state of «critical organs». At the stage I of CRT regimen, conformal irradiation on pelvis minor was delivered at the electron linear accelerator «Clinac 2100 CD» with an energy of 6 MeV per area of pelvis minor with single radiation dose (SRD) of 2.0 Gy and total radiation dose (TRD) of up to 46 Gy. Patients in the study group received the CRT along with administration of chemoradiomodifying agent cisplatin 40 mg/m2 once a week intravenously (drip-feed), patients in the comparison group received no radiomodifier. At the stage II of CRT regimen, an intracavitary brachytherapy (ICBT) was administered to the CC patients at the gamma therapy equipment «AGAT-VU» using 60Co (high dose rate – HDR) sources in the mode of SRD of 5 Gy 2 times a week, 7–8 fractions, and TRD of 35–40 Gy at p. A. The TRD in total was 77–89 Gy at the p. A and 54–60 Gy at p. B. Administration of cisplatin 40 mg/m2 at the stage II of CRT was continued in the study group once a week intravenously (drip-feed), total dose of up to 200–300 mg. Radiobiological studies were performed on the peripheral blood samples from the CC patients (n = 39) before and after ChRT. The control group consisted of healthy women of the appropriate age. Blood was sampled into the special 6 ml Vacutainer type tubes with an anticoagulant according to the manufacturer’s instructions (BioReagent). Intensity of generation of О• 2– in PBL was evaluated by the chemiluminescence method using the lucigenin indicator, which, as a result of reacting with О• 2–, emits light quanta recorded by the device. Measurements were carried out on the AutoLumat LB 953 device (Germany) with appropriate corrections made to the methodology. Results and discussion. Effectiveness of CRT in CC patients was evaluated according to regression of the primary tumor focus (clinical, ultrasound, MRI or SCT data) and presence/absence of toxic manifestations of treatment following the criteria for evaluating the solid tumors regression according to the Response Evaluation Criteria in Solid Tumor (RECIST). Conclusions. The results of the study indicate that chemoradiotherapy contributes to pronounced regression of cervical tumors and does not increase toxicity of treatment due to timely correction of complications.