Purpose: Imatinib mesylate transformed the treatment and paradigms of chronic myeloid leukemia. European LeukemiaNet (ELN) group has defined specific treatment milestones with an optimal outcome to be achieved in patients.
Methods: In a retrospective cohort study, we evaluated the impact of clinical and biological variables on achieving an optimal response at 6 and 12 months according to ELN recommendations. We included 106 patients with chronic phase chronic myeloid leukemia (CML) with appropriate bone marrow aspirate and biopsy for immunohistochemistry.
Results: The number of white blood cells (WBC), the percentage of peripheral blast, the values of Sokal and ELTS scores and the percentage of Ki-67+ cells in the bone marrow predicted a complete cytogenetic response (CCyR) at 6 months, but only WBC and EUTOS score predicts CCyR at 12 months. We found that Sokal score below 0.775 was very sensitive to achieve of CCyR at 6 months (m) and that all patients with a value <0.550 achieved CCyR-6m. Patients with a low percentage of blast in the peripheral blood (≤1.5%) or in the bone marrow (≤5%) together with lower WBC (≤100×109/L) were likely to have significantly higher CCyR rates at 6 and 12 months respectively. Also, patients with a higher number of Ki67+ cells in the leukemic areas of the bone marrow had a significantly better outcome. Unfortunately, our investigation did not reveal that bone marrow fibrosis (MF grade), microvascular density, percentage of CD34+, CD61+ or PTCH1+ cells could have any effect on achievement of CCyR at 6 or 12 months.
Conclusion: Our investigation has shown that only a few biological characteristics in patients with CML can predict the optimal treatment outcome after imatinib.