The combination of Fludarabine and Cyclophosphamide have yielded overall response rates of over 80% in previously untreated patients with indolent Non-Hodgkin-Lymphoma. However, hematotoxicity rates were high with Grade 3 and 4 toxicities of over 50%. Several studies have indicated that the treatment with Pentostatin and Cyclophosphamide causes lower hematotoxicity rates than the combination of Fludarabine and Cyclophosphamide. To evaluate the efficacy and safety of treatment with Pentostatin/Cyclophosphamide immuno-chemotherapy for patients with newly diagnosed or relapsed Immunocytoma/Morbus Waldenström, B-cell chronic lymphocytic leukemia (B-CLL) and other indolent CD20-positive B-NHL, an open, non-randomized, multi-center prospective phase II-study to evaluate the efficacy and safety of treatment with immuno-chemotherapy is conducted. Treatment consists of 6 courses of Pentostatin (4mg/m² on day 1), Cyclophosphamide (600mg/m² on day 1) and Rituximab (375mg/m² on day 0) administered every three weeks. Patients achieving complete or partial remission undergo maintenance therapy consisting of 8 courses of Rituximab (375mg/m²) administered every three months over a period of 2 years.

Inclusion Criteria:

• confirmed first diagnosis of or relapsed CD20-positive Immunocytoma, B-CLL or other indolent B-NHL
• therapy-requiring CLL defined as: Binet stage C or Binet B combined with occurence of B-symptoms, rapidly progressing disease, risk of organ compression by lymphoma mass
• therapy-requiring Immunocytoma as defined by the Consensus Panel Recommendations from the Second International Workshop on Waldenström´s Macroglobulinemia, 2003)
• age > 18 years
• anticipated life expectancy > 6 months
• ECOG 0-3
• no significant comorbidities
• signed informed consent
• efficient method of contraception during time of therapy (men and women)

Exclusion Criteria:

• age < 18 years
• CD20 negativity
• significant comorbidities interfering with therapy as required by the protocol
• history of HIV infection or active hepatitis