Increase in platelet count in older, poor-risk patients with acute myeloid leukemia or myelodysplastic syndrome treated with valproic acid and all-trans retinoic acid

BACKGROUND. The authors investigated the efficacy and safety of the histone deacetylase inhibitors valproic acid (VPA) and all-trans retinoic acid (ATRA) as differentiation agents in a cohort of older, poor-risk patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). METHODS. Twenty older patients with recurrent or refractory AML or MDS were treated in a Phase 11 protocol with sequential VPA and ATRA therapy. VPA was started at a dose of 10 mg/kg per day and then escalated to achieve the serum concentration of 45-100 mu g/mL. ATRA was added at 45 mg/square meters (sm) per day when VPA reached the target serum concentration. Only patients treated continuously for 2 months were considered evaluable. RESULTS. Hematologic improvement, according to World Health Organization criteria, was observed in 6 of 20 patients enrolled in the protocol but in 6 of 11 considered evaluable. In five patients, a major platelet response was observed, achieving platelet transfusion independence. Three of these five patients also exhibited a minor erythroid response. A sixth patient showed both a minor erythroid response and a platelet response. The median duration of response was 189 days (range, 63-550 days). No significant reduction in the blast count was observed. Grade 3 neurocortical toxicity was observed in four patients. Severe bone pain was experienced by 4 patients (2 Grade 4 and 2 Grade 3) and was associated with an increase in the peripheral blast cell count. Treatment with ATRA did not modify the response observed with VPA alone. CONCLUSIONS: Differentiation therapy with VPA was of clinical benefit in approximately 30% of elderly patients with AML and MDS of the refractory anemia with excess of blast type with unfavorable prognostic features. A striking platelet transfusion independence lasting several months may be obtained in some patients, reducing the burden of palliative care and improving the quality of life. (c) 2005 American Cancer Society.