CHRONIC MYELOID LEUKEMIA COURSE IN PERSONS EXPOSED TO IONIZING RADIATION AS A RESULT OF THE CHORNOBYL ACCIDENT.

Objective. Describe and characterize the peculiarities of the chronic myeloid leukemia (CML) course and response to treatment in patients irradiated as a result of the Chornobyl nuclear power plant (ChNPP) accident based on the assessment of clinical-laboratory and clinical parameters. Materials and methods. The CML patients (n = 33) exposed to ionizing radiation as a result of the ChNPP accident were enrolled. The comparison group consisted of CML patients (n = 725) with no history of radiation exposure. All patients were in the chronic phase of the disease. Clinical, hematological and molecular genetic research methods were applied. Results. Patients exposed to ionizing radiation as a result of the ChNPP accident had no differences in CML manifestation, as well as in classical genetic markers at the onset of the disease compared with patients with no history of radiation exposure. Reduction of tumor clone on imatinib therapy was significantly less effective in the patients exposed to ionizing radiation than in cases of no history of radiation exposure. Cases of primary resistance were statistically significantly prevalent in the ChNPP accident consequences clean-up workers while in the residents of radiologically contaminated areas a statistically significant increase in probability of loss of complete cytogenetic response (development of secondary resistance) to imatinib therapy was found. An association was found between the radiation exposure and probability of loss of complete cytogenetic response to imatinib therapy in this group of patients. Conclusion. The radiation exposure in the history even many years before the onset of CML is an unfavorable exogenous factor responsible for the development of resistance to imatinib therapy. Key words: chronic myeloid leukemia, ionizing radiation, tyrosine kinase inhibitors, response to treatment.