Objective: To report disease transformation in 3 imatinib mesylate treated Philadelphia chromosome-positive chronic myelogenous leukemia (Ph(+)CML) patients who achieved cytogenetic response.
Methods: Hematologic examinations and bone marrow G-banding karyotyping were evaluated at regular intervals in 3 patients with Ph(+)CML who achieved hematologic responses during continuous imatinib therapy, including 1 patient in first chronic phase (case 1), 1 patient in second chronic phase (case 2) and 1 patient in accelerated phase (case 3).
Results: Case 1, case 2 and case 3 achieved complete cytogenetic response after 4, 3 and 6 months of imatinib therapy respectively. Though under continuously imatinib treatment, they developed acute lymphoblastic leukemia, acute myelogenous leukemia and extramedullary blast crisis in the following 12, 6 and 0 months respectively. Cytogenetic studies of bone marrow in the crisis period showed that cells in case 1 and case 3 had a complete cytogenetic response (Ph(+)cell=0), but case 2 had 20% Ph(+) cells.
Conclusion: Acute leukemia or extramedullary blast crisis with Ph(-) cells or dominant Ph(-) cells in bone marrow may occur in the patients with Ph(+)CML after imatinib therapy.