A PILOT-STUDY OF ISOTRETINOIN IN THE TREATMENT OF JUVENILE CHRONIC MYELOGENOUS LEUKEMIA

Background. Juvenile chronic myelogenous leukemia (CML) is a rare myeloproliferative disease of infants and young children for which there is no effective therapy other than allogeneic bone marrow transplantation. In vitro, isotretinoin (13-cis-retinoic acid) attenuates both the spontaneous proliferation of leukemic peripheral-blood progenitor cells (granulocyte-macrophage colony-forming units) and their selective hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF). We conducted a pilot study to evaluate the clinical efficacy of isotretinoin in juvenile CML. Methods. To be eligible the patients had to have newly diagnosed untreated disease, leukocytosis with monocytosis, marrow with less than 25 percent blasts, hepatosplenomegaly, no chromosomal abnormalities, and negative viral cultures and antibody titers. Isotretinoin was administered orally in single daily doses of 100 mg per square meter of body-surface area. When possible, patients subsequently underwent bone marrow transplantation. Results. Ten children (median age, 10 months) were enrolled in the study. In all 10 there was spontaneous colony formation of leukemic progenitor cells in vitro. In the eight patients tested there was hypersensitivity to GMCSF. The only toxic effect of isotretinoin therapy was cheilitis in two patients. Four children had disease progression. Two children had complete responses to isotretinoin (normalization of the white-cell count and disappearance of organomegaly), three had partial responses (more than a 50 percent reduction in the white-cell count and degree of organomegaly), and one had a minimal response (more than a 50 percent reduction in the white-cell count, but a 26 to 50 percent reduction in the degree of organomegaly). The median duration of response was 37 months (range, 6 to 83). Three of the four children who had a complete or partial response and who did not undergo bone marrow transplantation were alive 36 to 83 months after the diagnosis of juvenile CML. The spontaneous colony formation in vitro was reduced in samples from the five patients in whom this factor was reassessed during treatment. There was also a reduction in the hypersensitivity of leukemic progenitor cells to GM-CSF in the two patients retested. Conclusions. Isotretinoin can induce durable clinical and laboratory responses in patients with juvenile CML.