Immunotherapy with the monoclonal anti-CD20 antibody rituximab has become standard of care for patients with follicular lymphoma. However, there are still open questions regarding dosing and scheduling of rituximab, optimal type of chemotherapeutic combination partners during induction as well as the best interval and length of rituximab maintenance treatment. Fludarabine-mitoxantrone combinations have shown strong debulking activity as initial therapy followed by rituximab maintenance. While rituximab maintenance with a standard dose of 375 mg/m2 prolongs clinical remissions, administration schedules still vary: Three-monthly infusions for 2 years and two-monthly infusions for one or 2 years are most frequently used. A few pharmacokinetic data for rituximab have been reported for induction treatment. These studies have proposed a presumptive "active" level of 25.000 ng/ml in anti-lymphoma treatment. However, there is only limited information regarding maintenance treatment in patients who are in remission and have no remaining tumor load.

The aim of this trial is to investigate the effect of treatment with oral Fludarabine, Mitoxantrone und Rituximab and Rituximab maintenance on the depth of remission measured by BCL2/IgH PCR.

Inclusion Criteria:

• a positive BCL2/IgH rearrangement in peripheral blood (PB) and/or bone marrow (BM)
• clinical stage III or IV, requiring treatment with one or more of the following criteria: symptoms related to the disease, hemoglobin less than 12 g/dL, platelets less than 100 G/L, progressive disease, bulky tumor of more than 10 cm

Exclusion Criteria:

• pretreatment