Rituximab and Combination Chemotherapy Combined With Yttrium Y 90 Ibritumomab Tiuxetan in Treating Older Patients With Previously Untreated B-Cell Lymphoma

DISEASE CHARACTERISTICS: Histologically confirmed diffuse large B-cell lymphoma, including any of the following subtypes: Centroblastic Immunoblastic T-cell/histiocyte-rich Lymphomatoid granulomatosis type Anaplastic large B-cell Plasmablastic Mediastinal Intravascular large B-cell lymphoma Previously untreated High-intermediate or high-risk disease, defined by an age-adjusted international prognostic index score of 2 or 3 (with 1 point each assigned for a ECOG greater than 1/Karnofsky less than 80%, lactate dehydrogenase greater than normal, and stage III or IV) Lymphomas with discordant histology and a diffuse large B-cell component are eligible Must have an initial diagnostic specimen that is CD20+ At least Ann Arbor stage II disease No confinement of disease to an involved-field radiotherapy port (stage I or limited stage II disease) Bidimensionally measurable disease with at least 1 lymph node at least 2.0 cm by 2.0 cm by physical examination, CT scan, or positron-emission tomography Bone marrow cellularity greater than 15% No known brain or leptomeningeal metastases No primary effusion lymphomas PATIENT CHARACTERISTICS: Age 60 and over* NOTE: *Patients 60 to 65 years of age must be deemed ineligible for autologous stem cell transplantation Performance status Karnofsky 50-100% Life expectancy Not specified Hematopoietic Not specified Hepatic Bilirubin no greater than 2.0 mg/dL (except for Gilbert's disease) Renal Creatinine no greater than 1.5 mg/dL* OR Creatinine clearance greater than 50 mL/min* NOTE: *Patients not meeting either criterion but who have renal insufficiency directly related to lymphomatous involvement of the kidneys or renal collecting system are allowed Cardiovascular Cardiac ejection fraction at least 50% by echocardiogram No acute myocardial infarction within the past 3 months No uncontrolled hypertension No New York Heart Association class III or IV congestive heart failure No unstable angina pectoris Other Not pregnant or nursing Fertile patients must use effective contraception HIV negative B12 and folate greater than the lower limit of normal Transferrin saturation at least 15% Ferritin greater than 10 µg/L At least 6 weeks since prior RBC donation No active seizure disorder Prior seizure disorder allowed if free of antiseizure medication and evidence of seizure activity for the past 5 years No concurrent uncontrolled medical problems that would preclude administration of chemotherapy or radioimmunotherapy No other concurrent malignancy treated with chemotherapy or radiotherapy except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix PRIOR CONCURRENT THERAPY: Biologic therapy At least 4 weeks since prior RBC transfusion No prior biologic therapy No other concurrent biologic therapy Chemotherapy No prior chemotherapy (one course of R-CHOP allowed) No other concurrent standard or investigational chemotherapy Endocrine therapy No more than 7 consecutive days of prior steroids (premedication allowed for prior intravenous contrast allergy) No other concurrent corticosteroids Radiotherapy No prior radiotherapy Surgery Not specified