1. Efficacy: The primary objective (primary endpoint) is to determine the rate of response (partial or complete response) at week 16 (± 2) post-treatment in both pilot arms: the high dose Rituximab (or HDR) group (750 mg/m2 x 4) and the group treated with a regimen combining standard doses of Rituximab with CVP (R-CVP.) A complete response (CR) will be a platelet count increase ³ 150,000/mL on two consecutive occasions one week apart, without any other therapy. A partial response will be considered if the platelet count increases between 50 and 150,000/mL.