Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically proven hairy cell leukemia (HCL)

- Classic HCL

- Hairy cells in the bone marrow and/or peripheral blood which co-express
CD20/CD25 or CD20/CD11c, and/or which are positive for tartrate resistant
acid phophatase (TRAP)

- Prolymphocytic HCL variant

- Lymphoid cells in the bone marrow and/or peripheral blood with morphology
intermediate between typical hairy cells and prolymphocytes, which
co-express CD20/CD11c but lack CD25 expression, and which are negative for
TRAP

- Progressive or recurrent disease after prior treatment with cladribine

- Greater than 1 month since standard dose cladribine OR

- Greater than 3 months since low dose cladribine

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- WHO 0-2

Life expectancy:

- At least 3 months

Hematopoietic:

- Not specified

Hepatic:

- Bilirubin no greater than 2.0 mg/dL

Renal:

- Creatinine no greater than 2.3 mg/dL

Cardiovascular:

- No serious cardiac disease

Other:

- No acute or chronic infection

- HIV negative

- No psychosis

- Not pregnant or nursing

- No other prior or concurrent malignancy except carcinoma in situ of the cervix or
basal cell or squamous cell skin cancer

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Not specified

Chemotherapy:

- See Disease Characteristics

- Recovered from prior chemotherapy

Endocrine therapy:

- Not specified

Radiotherapy:

- Not specified

Surgery:

- Not specified

Other:

- Recovered from prior therapy

- No concurrent cytoreductive therapy