Prediction of optimal cytogenetic responses at 6 and 12 months in patients with chronic myeloid leukemia in chronic phase treated with imatinib.

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.