Features of cytogenetic effects in oncological patients during radiotherapy with prior radiation exposure

Abstract

Background. Radiotherapy can be used numerous times for treating oncological patients as one of the most effective ways of fighting against cancer. However, there is limited data on the effect of prior radiation exposure on the further development of cytogenetic alterations under the influence of radiological factors. Primary radiation treatment, as well as the second one, is an example of a complex scenario of fractionated irradiation, examination of which is of fundamental and practical importance for understanding complex processes of formation and elimination of cytogenetic markers of radiation exposure for further improvement of biodosimetry system and development of personalised radiotherapy. Purpose. To determine the nature of changes of radiation-induced cytogenetic alterations and genomic disorders in patients with lung, head and neck cancer during radiotherapy on the background of prior radiation exposure. during radiotherapy with prior radiation exposure. Materials and methods. 29 oncological patients with lung, head and neck cancer were examined. 16 of them received radiotherapy for the first time, and 13 – for the second. We studied chromosome aberration frequency and genomic disorders during external beam radiation therapy by cytogenetic test. Results. In the patients pre-irradiation level of cytogenetic injuries exceeded spontaneous level. In addition, chromosome aberration frequency in the patients, who had received prior radiation exposure, was significantly higher than those who had not been treated with radiotherapy. It depended on the period between radiotherapy treatment courses. The increase in level of radiation-induced cytogenetic injuries during the whole radiotherapy treatment course of patients was observed, regardless of prior therapeutic exposure. Under quite a high level of chromosome damage in the group of secondary patients at the beginning of the treatment, chromosome aberration increase rates were higher than in the group of the primary patients. The distribution of markers of radiation exposure over cells during radiotherapy was overdispersed according to Poisson statistics in both of the groups. The changes in the frequency of genomic disorders were mostly of fluctuating nature. Conclusions. In the secondary patients, the level of cytogenetic indexes before radiotherapy exceeded the indexes of the primary patients. The level of chromosome damage increased during the radiotherapy treatment course in both primary and secondary patients, but at different rates. The additional genotoxic effect of reirradiation manifested itself only in a greater maximum quantity of aberrations per aberrant cell in the secondary patients. In terms of increased rates of cytogenetic injuries, a more significant genotoxic effect from the second radiotherapy on the background of prior radiation exposure was not detected.