Application of low-dose etoposide therapy for myelodysplastic syndromes.

The therapy for myelodysplastic syndromes (MDS) and acute leukemia (AL) transformed from MDS is not well established. Etoposide (VP 16-213) at low concentrations shows differentiation-inducing activity against leukemic cells in vitro. A prior study showed that oral low-dose etoposide therapy was effective in patients with chronic myelomonocytic leukemia. We used low-dose etoposide to treat six patients with refractory anemia with excess blasts in transformation (RAEB-t) and seven patients with AL transformed from MDS. The etoposide (50 mg, 2-7 times/week) was usually administered intravenously to ensure reliable bioavailability. Of 12 assessable patients, four RAEB-t patients achieved a partial response and one AL patient achieved complete remission. The responders became transfusion-independent, and this continued for 2-9 months while etoposide therapy was continued. Three of five responders had been resistant to prior repeated low-dose cytarabine therapy. The side effects were mild and well tolerated. Heterogeneous mechanisms were surmised to explain the clinical effects of low-dose etoposide. Several aspects, including the optimal schedule of low-dose etoposide therapy, the effect of this therapy on the patients' survival, the usefulness of combination therapy with other chemotherapeutic drug(s) and/or cytokine(s), should be investigated in the future.