The role of imatinib's side effect of cytopenia in predictioning the activity of the treatment in patients with diagnosis of gastrointestinal stromal tumor

During the use of tyrosine kinase inhibitors, some side effects can be seen related to the inhibition of the target gene or pathway. Imatinib, a tyrosine kinase inhibitor that inhibits c-kit, can also cause cytopenia by inhibiting c-kit. This study aims to evaluate the role of cytopenia side effects of imatinib, a tyrosine kinase inhibitor, in predicting treatment efficacy. Patients followed up with the diagnosis of GIST in the Medical Oncology Clinic of Gaziantep University Faculty of Medicine were retrospectively scanned. A total of 61 patients who were started on imatinib therapy with the diagnosis of metastatic or unresectable GIST were included in the study. The blood count values of the patients 3 months before the imatinib treatment and within 3 months after the treatment was started were recorded. The group with 0.8 g/dL decrease in hemoglobin value, 500/µL decrease in total leukocyte, lymphocyte and neutrophil values or 50.000/µL decrease in platelet value compared to the baseline value and the group without decrease were analyzed by Kaplan-Meier for progression-free survival (PFS). Although the most common localization is the stomach, atypical localized tumors such as retroperitoneal and different localizations of the gastrointestinal tract were also encountered. Patients with PDGFRA mutation were detected with the C-kit. The mean age was 69. Twenty-three of the patients were women (37.7%). The median follow-up was 52(41.3-62.7) months. The median PFS was 33(20.2-45.8) months. The median PFS of patients with a decrease of 0.8 g/dL in hemoglobin after imatinib treatment was 46.0(32.5-59.5) months, while that of patients who could not fall was 21.0(10.1-31.9) months (P=0.008). However, no correlation was observed between decrease in leukocyte, lymphocyte, neutrophil and thrombocyte levels, which are other parameters, and progression-free survival. Decrease in hemoglobin value may be a positive predictive parameter for PFS in GIST patients treated with imatinib. Keywords: GIST, prognostic factors, survival, cytopenia, tyrosine kinase inhibitors