For patients with advanced disease (R3/R4) it is tested whether the event-free survival can be improved by adding rituximab to the standard chemotherapy. Two different rituximab regimens will be evaluated in a randomized design: Patients in the standard arm will receive one dose of rituximab as monotherapeutic agent in the rituximab window R five days prior to the start of standard chemotherapy. Patients of the rituximab plus arm will receive the rituximab window and additional six doses of rituximab added to the first four courses of chemotherapy. In addition the immune reconstitution will be analyzed comparing the effect of the two regimens of rituximab added to standard chemotherapy.