Chronic myeloid leukemia is a malignant clonal disease classified as a myeloproliferative neoplasm. It is defined by a translocation between chromosomes 9 and 22, resulting in the formation of the BCR::ABL1 fusion gene. Determination of the expression level of the fusion gene allows us to monitor the response to treatment with tyrosine kinase inhibitors. Early molecular response after 3 months of treatment is an important prognostic factor. The halving time or rate of decline in the number of copies of the fusion gene is a potential predictor of disease outcome. The halving time is not yet used in routine clinical treatment of patients and for patients in Slovenia halving times were not yet calculated.
The purpose of the master's thesis was to calculate the halving time and define its influence on the parameter of treatment success. As part of the master's thesis, we collected data on patients with chronic myeloid leukemia in Slovenia for a 10-year period (2011-2021). The data we collected were: gender and age of the patients, date of initiation of treatment, level of expression of the fusion gene at different time periods, molecular responses at different time periods, type of initial treatment, spleen size and differential blood count results. From data we collected, we calculated the relative risks according to the EUTOS and ELTS scores.
The results of the statistical analysis show that patients with better molecular response after one year of treatment have shorter halving times, which indicates better response to the treatment. Patients who received second generation inhibitors as initial treatment also have shorter halving times. From the statistical analysis, we discovered that among patients with different transcripts (e13a2 or e14a2), the halving times are not statistically different and that the halving times of patients with different relative risks according to the ELTS score are not statistically different. We also discovered there is moderate correlation between the halving times and the expression levels of the BCR::ABL1 fusion gene in an international scale after one year of treatment. In the future, halving time could become a new early predictor of the outcome of the disease, which would enable better individual treatment for patients, and would allow doctors to make easier decisions about the appropriate treatment early after the diagnosis.
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