Mini-ICE Protocol is Better Than High-Dose Hydroxyurea to Mobilize Ph-Negative Cells in Earlier Phases of Chronic Myelogenous Leukemia

Abstract

We refer to the recent paper by Johnson et al.^[1] regarding the use of high-dose hydroxyurea to mobilize Ph-negative progenitor cells. We have already dealt with this topic in the report of our results with ICE and mini- ICE^[2]. In that occasion, we showed that these protocols were able to determine the mobilization of Ph-negative cells even in patients cytoge-netically refractory to IFN-α and/or in advanced phases of disease. These results were recently confirmed by an international study^[3]. Generally speaking, these protocols gave better results when employed in earlier phases of disease; moreover, mini-ICE protocol proved to be extremely well tolerated, administered in many patients on an outpatient basis and of capable obtaining the same cytogenetic results as the ICE protocol^[4]. From the update reported by Johnson et al., no improvement occurs with respect to the previous one published in 1996^[5] mainly in respect to the complete failure of this protocol to harvest complete or partial Ph-negative collections. The last 8 patients added to the previous paper indicate that no complete or partial diploid cells were obtained. In the attempt to verify if the results could be better in the earlier phases of disease, we compared Johnson's data^[1] with our recently published results^[3] (Table I). Nineteen patients were treated with mini-ICE protocol and 8 patients with high-dose hydroxyurea. Notwithstanding the fact that the Sokal index was missing in the Johnson's group, a great difference in the Ph-negative collections was found. Mini-ICE was effective in a rate of 80% (complete + partial) versus 36% with hydroxyurea; if only the Ph-negative collections are considered, mini-ICE was effective in 10 patients (53%) versus 1 patient (12%) with hydroxyurea. Two patients failed to collect PBPC in hydroxyurea group, but no one failed in the mini-ICE group. All patients were PCR positive in the hydroxyurea group while the major part of Ph-negative phereses in the mini-ICE group had an hybrid BCR-ABL transcript ≤10³/µg according to quantitative RT-PCR^[6].