Rituximab and Cladribine in Treating Patients With Newly Diagnosed Non-Hodgkin's Lymphoma

DISEASE CHARACTERISTICS: Histologically confirmed mantle cell lymphoma* Measurable or assessable disease defined as at least one of the following: Lymph node or tumor mass that is 2.0 cm or more in at least one dimension by CT scan, MRI, or plain radiograph imaging OR greater than 1.5 cm in at least one dimension by physical exam Splenic enlargement, if the spleen is palpable, at least 3 cm below the left costal margin Diffuse infiltration of an organ such as the stomach, bone marrow, peripheral blood, liver, lungs, or bowel by lymphoma without a discrete mass would constitute assessable, but not measurable, disease No known CNS involvement NOTE: *If tumor tissue is unavailable for biopsy, blood or bone marrow specimens may be used to establish patient eligibility provided fusion signals indicate the presence of t(11;14)(q13;q32) by fluorescence in situ hybridization using CCND1/IGH AND mantle cell lymphoma involvement is determined by morphology PATIENT CHARACTERISTICS: Age 18 and over Performance status ECOG 0-3 Life expectancy At least 12 weeks Hematopoietic Absolute neutrophil count at least 1,500/mm^3 Platelet count at least 100,000/mm^3 Hepatic Total or direct bilirubin no greater than upper limit of normal (ULN) (with or without secondary liver involvement) SGOT no greater than 3 times ULN (5 times ULN if there is liver involvement) Renal Creatinine no greater than 2.0 mg/dL Cardiovascular No myocardial infarction within the past 6 months No uncontrolled high blood pressure No unstable angina No serious uncontrolled cardiac arrhythmia No active congestive heart failure Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for 30 days after study participation HIV negative No other malignancy within the past 5 years except carcinoma in situ of the cervix, resected basal cell or squamous cell skin cancer, or prostate cancer that is in remission after a radical retropubic prostatectomy or radiotherapy No medical or psychiatric condition that makes the patient a poor risk for this study No active or uncontrolled infection No known hypersensitivity to rituximab or its components or to murine proteins PRIOR CONCURRENT THERAPY: Biologic therapy No prior biologic therapy for mantle cell lymphoma Chemotherapy No prior chemotherapy for mantle cell lymphoma Endocrine therapy No prior endocrine therapy for mantle cell lymphoma Radiotherapy No prior radiotherapy Surgery Prior splenectomy allowed (for diagnosis, cytopenia, or symptomatic splenomegaly)