Thalidomide in multiple myeloma, myelodysplastic syndromes and histiocytosis. Analysis of clinical results and of surrogate angiogenesis markers

Background: Thalidomide, as a single agent, has been recently found to induce a clinical response in one third of refractory or relapsed myeloma patients. Although it has been reported that thalidomide significantly inhibits angiogenesis, it is still unclear whether its clinical effect is mediated, at least in part, by its anti-angiogenic properties. Patients and methods: We evaluated thalidomide as a single agent in myeloma, myelodysplastic syndromes (MDS) and histiocytosis, i.e. hematological diseases characterized by increased angiogenesis, and measured prospectively a number of surrogate angiogenesis markers. Results: Clinical responses were observed in 7 of 17 myeloma and 2 of 5 MDS patients. The histiocytosis patient had a partial response. At the time of the best clinical response, plasma levels of angiogenic growth factors, vascular endothelial growth factor (VEGF) and basic-fibroblast growth factor (b-FGF), were significantly decreased, and flow cytometry indicated a decrease of activated endothelial cells in the bone marrow of responding MDS patients. Conclusions: These observations confirm thalidomide efficacy in myeloma, suggest a possible use in MDS and histiocytosis and may contribute to the prediction of clinical response and to understanding the mechanism of thalidomide's action.