The use of iridium-192 ionising radiation in radiotherapy for patients with gynaecological cancer
Ivankova V.S., Domina E.A., Khrulenko T.V., Baranovska L.M.
Summary. The use of the latest radiation technologies in brachytherapy, utilising high-dose-rate sources of cobalt-60 (60Co) and iridium-192 (192Ir) in modern treatment protocols for patients with gynaecological cancers, enables optimal dose distribution within the clinical target whilst minimising radiation exposure to surrounding organs and tissues. This technique involves irradiating large volumes whilst delivering high therapeutic doses at the tolerance limits of «critical» organs (the bladder and rectum) and tissues. A key challenge in modern radiation oncology remains the minimisation or prevention of early and late radiation-induced complications, the prolongation of life expectancy and the improvement of quality of life; this remains a complex task which, alongside the physical and technical characteristics of ionising radiation sources, requires the development of radiobiological criteria. Taking into account the fundamental radiobiological principles will ensure further progress in radiation oncology. With the aim of studying and comparing the biological effects of 192Ir with those of the reference gamma radiation source 60Co, and of improving the efficacy of brachytherapy using a 192Ir source, radiobiological dosimetry was carried out using a test system based on peripheral blood lymphocytes from gynaecological cancer patients, followed by cytogenetic analysis of radiation-induced chromosomal aberrations. Radiation markers — dicentric chromosomes with an accompanying paired fragment — predominated in the spectrum of radiation-induced damage. Materials and methods. With regard to the clinical aspect, the Department of Radiation Oncology at the National Cancer Institute carried out comprehensive conservative treatment of 72 patients with stage II–III secondary cervical cancer (SCC), T2-3N0-1M0, who underwent combined radiotherapy. In the main group (37 patients), during the brachytherapy phase, treatment was administered using 192Ir radiation sources via a high-dose-rate (HDR) apparatus. In the control group (35 patients), HDR brachytherapy was administered using 60Co sources. Results. Brachytherapy using high-power 192Ir and 60Co sources on modern, high-tech equipment ensures high precision in dose distribution when irradiating malignant tumours, minimises the radiation exposure to «critical» tissues, and improves treatment outcomes. The use of 192Ir, compared with 60Co, increases the throughput of patient treatment, enhances tumour regression, and reduces the incidence of radiation reactions in critical organs. We carried out radiobiological studies at the genetic, biochemical, biophysical and cytological levels of patients’ somatic cells with the aim of bioindicating radiation damage caused by the radioisotope 192Ir. Conclusions. Continuing clinical trials with radiobiological monitoring will make it possible to predict early and late radiation-related complications and, thereby, ensure a personalised approach to brachytherapy for patients with gynaecological cancers using a 192Ir gamma-ray source.
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