Treatment outcome of the tyrosine kinase inhibitor (bosutinib) in previously treated chronic myeloid leukemia patients (sample of Iraqi patients)

Chronic myeloid leukemia (CML) is a type of myeloproliferative neoplasm characterized by the excessive accumulation of malignant myeloid cells in the bone marrow and peripheral blood. This condition is primarily triggered by a specific chromosomal translocation known as t(9;22) (q34.13;q11.23), which leads to the formation of the BCR-ABL fusion gene. The treatment landscape for CML has undergone significant changes with the approval of tyrosine kinase inhibitors (TKIs) targeting the BCR-ABL1 kinase activity. One such inhibitor is bosutinib, which has been available for several years to treat patients with chronic, accelerated, and blast-phase CML who have shown resistance or intolerance to previous therapies. The aim of this study was to assess efficacy and safety of Bosutinib as a 2nd line therapy in CML patients, in addition to effect of adherence to treatment on patients response. Eighty-five patients with CML were enrolled in a prospective cohort study from October 2021 to October 2022 at Hematology Center in Medical City Complex – Baghdad. All patients failed to at least one TKI, and all of them started escalated dose of bosutinib. The patients were followed-up by assessing molecular and cytogenetic response at 3 and 6 months and monitored carefully for adverse events (AEs) which were graded by common terminology IX criteria for AEs version 5. Adherence to bosutinib was also monitored by a specific adherence scale to optimize the response rate to treatment. The mean age of patients was 47.3 ± 14.9 (range: 18–77), with male:female ratio 1.4:1. Status of CML patients showed that 89.4% were in the chronic phase, 5.8% in accelerated phase, and 4.7% in blast phase. Regarding the number of previous TKIs before bosutinib, 72.9% of patients failed to prior one TKI (imatinib). At 6 months (72.3%), patients achieve optimal response according to European Leukemia Net criteria 2013. Gastrointestinal symptoms and dermatological manifestations were the most common nonhematological AEs of bosutinib. According to 9-item Morisky Medication Adherence Scale, 42% of patients were adherent to medication which showed a significant association with a higher number of optimal response (P = 0.0001). Bosutinib is effective with a high and promising response as a subsequent line treatment in CML patients, and it is generally safe and associated with mild-to-moderate tolerable and manageable AEs. Adherence to the drug plays a significant role in optimal response to bosutinib.