RATIONALE: Drugs used in chemotherapy use different ways to stop cancer cells from dividing so they stop growing or die. Monoclonal antibodies, such as rituximab, can locate tumor cells and either kill them or deliver tumor-killing substances to them without harming normal cells. Combining chemotherapy with monoclonal antibody therapy may kill more cancer cells.

PURPOSE: Phase II trial to study the effectiveness of combining pentostatin, cyclophosphamide, and rituximab in treating patients who have chronic lymphocytic leukemia or other B-cell cancers that have been treated previously.

OBJECTIVES:

• Determine the dose of cyclophosphamide, with filgrastim (G-CSF) support, that can be safely administered with pentostatin and rituximab in patients with previously treated intermediate- or high-risk chronic lymphocytic leukemia or other low-grade B-cell malignancies. (Phase I closed to accrual effective 11/27/2001.)
• Characterize the toxicity of this regimen in these patients.
• Determine the incidence of response in these patients treated with this regimen.

OUTLINE: This is a multicenter, dose-escalation study of cyclophosphamide (CTX).

• Phase I: Patients receive CTX IV followed by pentostatin IV on day 1 of course 1. Patients also receive filgrastim (G-CSF) subcutaneously once daily beginning on day 3 and continuing until blood counts recover. During the second and subsequent courses, patients receive CTX IV, pentostatin IV, and rituximab IV on day 1. Patients also receive G-CSF as in course 1. Treatment repeats every 3 weeks for 3 courses in the absence of disease progression or unacceptable toxicity. Patients with at least a partial response after the third course receive an additional 3 courses.

Cohorts of 3-6 patients receive escalating doses of CTX until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which at least 2 of 6 patients experience dose-limiting toxicity.

(Phase I closed to accrual effective 11/27/2001.)

• Phase II: Patients receive CTX at the recommended phase II dose and treatment as above.

Patients are followed at least every 3 months for 1 year and then periodically thereafter.

PROJECTED ACCRUAL: A total of 3-30 patients will be accrued for the phase I portion of this study. (Phase I closed to accrual effective 11/27/2001.) A total of 14-30 patients will be accrued for the phase II portion of this study within 2.5 years.

DISEASE CHARACTERISTICS:

• Intermediate- or high-risk chronic lymphocytic leukemia (CLL) as defined by the three-stage Rai system

  • Rai intermediate disease must be active disease (including weight loss, fatigue, fevers, evidence of progressive marrow failure, splenomegaly, progressive lymphadenopathy, and progressive lymphocytosis with a rapid doubling time)

• Other low-grade B-cell neoplasms, including small lymphocytic lymphoma (and its variants), Waldenstrom's macroglobulinemia, and follicular lymphoma allowed

• Autoimmune hemolytic anemia or autoimmune thrombocytopenia allowed regardless of disease stage

• B-cells demonstrated by immunophenotypic (or immunohistochemical) analysis of the malignant lymphocytes

• Must be previously treated

• For CLL, absolute lymphocytosis in the blood at least 5,000 lymphocytes/mm^3 OR

• Bone marrow lymphocytosis at least 30% of all nucleated cells

• No Rai intermediate-risk disease that meets the criteria of Montserrat "smoldering leukemia" NOTE: A new classification scheme for adult non-Hodgkin's lymphoma has been adopted by PDQ. The terminology of "indolent" or "aggressive" lymphoma will replace the former terminology of "low", "intermediate", or "high" grade lymphoma. However, this protocol uses the former terminology.

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 60-100%

Life expectancy:

• More than 4 weeks

Hematopoietic:

• See Disease Characteristics

Hepatic:

• Bilirubin no greater than 2.0 mg/dL

Renal:

• Creatinine no greater than 2.0 mg/dL

Other:

• No active infections requiring systemic antibiotics
• Not pregnant or nursing
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 4 weeks since prior biologic therapy
• Concurrent intravenous immunoglobulin allowed
• Concurrent epoetin alfa allowed

Chemotherapy:

• At least 4 weeks since prior chemotherapy
• No other concurrent chemotherapy

Endocrine therapy:

• Concurrent prednisone therapy allowed as long as dose is stable or decreasing over the past 4 weeks
• No increase in prednisone therapy while on study

Radiotherapy:

• At least 4 weeks since prior radiotherapy
• No concurrent radiotherapy

Surgery:

• Not specified