Treatment of myelodysplastic syndromes with excess of blasts by bevacizumab is well tolerated and is associated with a decrease of VEGF plasma level

Abstract

Myelodysplastic syndromes (MDS) are associated with increased bone marrow vascularity and increased levels of various angiogenic factors including Vascular Endothelial Growth Factor (VEGF) which is implicated in the proliferation and survival of leukemic cells. Before the approval of hypomethylating agents in this indication, the GFM conducted a multicenter phase II trial testing the efficacy and tolerance of bevacizumab, a humanized monoclonal antibody against VEGF, in MDS with excess of marrow blasts and its impact on bone marrow angiogenesis. Twenty-one patients were enrolled (16 males and five females) with a median age of 70 years and 19 were evaluable for haematological response after treatment (5 mg/kg IV every 2 weeks for 12 weeks). WHO diagnosis at baseline was RAEB-1 (38%) and RAEB-2 (62%). Treatment was well tolerated and was associated with significant decrease of VEGF plasma level [median (low quartile-high quartile)] from 65.5 pg/ml [LQ (low-quartile)-HQ (high quartile), 35.3-87.3 to 30.4 pg/ml (LQ-HQ, 22.5-34.0 pg/ml)] (p < 0.01) and reduction of bone marrow angiogenesis from a median of 20 vessels/mm(3) (LQ-HQ, 16.5-33 vessels/mm(3)) to 15.5 vessels/mm(3) (LQ-HQ, 10-23.2 vessels/mm(3)) (p = 0.03). On the other hand, only one patient had a significant haematological response with achievement of RBC transfusion independence. Thus, although bevacizumab had a significant impact on VEGF levels and angiogenesis in our patients, very few responses were seen when this drug was used as single agent. Given its good tolerability profile, however, combination of bevacizumab with other drugs, especially hypomethylating agents, could be considered in MDS.