International Journal of Clinical Case Reports 2024, Vol.14, No.2, 79-86 http://medscipublisher.com/index.php/ijccr 83 therapy or shortly after the initiation of treatment. This may be due to pre-existing resistance mechanisms within the cells or the rapid loss of the initial response to treatment. The reasons for treatment tolerance and resistance are diverse. They may include intra-cellular genetic mutations, selective pressure induced by treatment, the presence of different subgroups within cancer cells, metabolic changes in treatment drugs, and so on. These factors enable cancer cells to adapt and overcome the effects of treatment. Overcoming treatment tolerance and resistance is a crucial research area. Scientists and doctors are making efforts to develop new treatment strategies to address these issues. This may involve the use of different therapeutic drugs or combination therapy approaches, personalized treatment plans, and a deeper understanding of the biological mechanisms behind tolerance and resistance. 3 Case Study Analysis 3.1 Application of Imatinib in chronic myeloid leukemia Imatinib is a tyrosine kinase inhibitor widely used in the treatment of chronic myeloid leukemia (CML) (Figure 3). It is a targeted therapy drug that disrupts the abnormal tyrosine kinase enzyme activity in leukemia cells, thereby inhibiting the progression of the disease. Figure 3 Myelogram of chronic myeloid leukemia Imatinib is a first-line treatment for chronic myeloid leukemia (CML) and is commonly used for newly diagnosed patients in the chronic phase of CML. It is the first targeted therapy successfully applied in the treatment of CML and is widely used in clinical practice. In CML patients, a specific chromosomal abnormality, known as the Philadelphia chromosome, is often present, leading to the production of the BCR-ABL fusion protein. This fusion protein has kinase activity, stimulating abnormal proliferation of leukemia cells. Imatinib works by inhibiting the activity of the BCR-ABL kinase, thereby interrupting its signaling and suppressing the growth of leukemia cells. The use of imatinib has significantly improved the survival rate and quality of life for CML patients. Most patients can maintain the chronic phase by continuously taking imatinib, and in first-line treatment, many patients can achieve sustained molecular and clinical responses. Imatinib is also used to treat early and accelerated phase CML, but treatment at these stages may require higher doses of imatinib or a switch to other targeted therapies (Song et al., 2023). Some patients may develop resistance to imatinib during treatment, meaning their leukemia cells start to lose sensitivity to imatinib. In such cases, doctors may consider adjusting the treatment strategy, such as increasing the dose of imatinib or trying other targeted therapy drugs, such as second and third-generation tyrosine kinase inhibitors.
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