Cladribine and Rituximab in Treating Patients With Hairy Cell Leukemia

PRIMARY OBJECTIVES: I. To demonstrate the efficacy in achieving complete response of combination of cladribine administered intravenously over 2 hours for 5 days followed by rituximab weekly for 8 weeks in patients with untreated or previously treated hairy cell leukemia. II. To examine the efficacy of rituximab to eradicate minimal residual disease (MRD) after cladribine therapy (as assessed by immunophenotyping of bone marrow and peripheral blood). III. To examine the effect of addition of rituximab to cladribine on the long term disease-free (DFS) and overall survival (OS) (as compared with historical controls). IV. To evaluate potential predictors of outcome including molecular and flow evaluations of MRD, as well as other potential molecular predictors such as v-raf murine sarcoma viral oncogene homolog B1 (BRAF). OUTLINE: Patients receive cladribine intravenously (IV) over 2 hours once daily (QD) on days 1-5 and rituximab IV once weekly for 8 weeks beginning on day 28 in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 3 months for 1 year.