A non-randomised dose-escalating phase II study of thalidomide for the treatment of patients with low-risk myelodysplastic syndromes: the Thal-SMD-2000 trial of the Groupe Français des Myélodysplasies.

Patients (n=47) with low-risk myelodysplastic syndrome were treated with thalidomide [200 mg/d, increased by 200 mg/d/4 weeks up to week 16]. Responses were evaluated according to the International Working Group criteria at week 16 for 39 patients who received at least 8 weeks of treatment. Twenty-three (59%) patients showed haematological improvement (HI): four major erythroid response (HI-EM), 15 minor erythroid response, six major neutrophil response, two major platelet response. Side effects caused 22/39 to stop thalidomide before week 16. Nine of 23 responders continued thalidomide after week 16 [19% of trial patients] with sustained response in eight of nine. Six reached week 56, including the four HI-EM patients [13% of trial patients]. Nineteen of 36 red blood cell transfusion-dependent patients (53%) showed erythroid response, but only four became transfusion-independent. Among the 23 responders, the median duration of response was 260 d (range 30-650). Responses were sustained in all patients except one, and were observed between week 4 and week 8 in 85% of patients, at doses ranging from 200 to 400 mg. Only two patients responded at 600 mg/d and none at 800 mg/d. No clinical characteristics of responding versus non-responding patients were identified. The erythroid response rate was identical in all cytogenetic subgroups, including 5q31.1 deletions. Pretreatment vascular endothelial growth factor levels were lower in responders compared with non-responders (P=0.004). Microvessel density (MVD) increased and apoptosis decreased in four of six and in all six responders studied respectively whereas MVD and apoptosis were unchanged in three non-responders.