Myelosuppressive chemotherapy to mobilize normal stem cells in chronic myeloid leukemia

Ten patients with Ph+ chronic myeloid leukemia (CML) were treated with idarubicin, cytarabine and etoposide followed by G-CSF to harvest Ph-negative progenitor cells. Six were in first chronic phase (CP1), and four beyond CP1. Between two and six aphereses (median 3, total 36) were performed starting 9-26 days (median 14.5) after chemotherapy when the leukocyte count was 0.6-4.7 x 10⁹/l (median 1.2), 1.3-3.6 x 10⁸ mononuclear cells/kg (median 2.8), 0-128.4 x 10⁴ CFU-GM/kg (median 1.2; seven patients) and 0.3-25.1 x 10⁶ CD34⁺ cells/kg (median 9.8; seven patients) were collected. Seven of 27 harvests showing metaphases were 100% Ph-negative, 11 partially Ph-negative, and nine were 100% Ph+. All three patients with 100% Ph-negative collections were in CP1 and within 4-26 months of diagnosis. Four of six CP1 patients showed significant cytogenetic response compared with none of four beyond CP1 (P = 0.036). The absolute neutrophil count remained < 0.5 x 10⁹/l for 9-44 days (median 15.5) following chemotherapy. Four patients (three Ph-negative) were autografted after 16 mg/kg busulfan (n = 2) or 200 mg/m² melphalan (n = 2). One of the three patients receiving Ph-negative cells died of graft failure, and two are alive with 15% and 50% Ph-negative cells at 15 and 11 months on interferon-α. We conclude that it is possible to harvest Ph-negative cells after myelosuppressive chemotherapy in some CML patients treated early in the course of CP1. However, in view of lack of consistent response, investigation of alternative approaches is necessary.