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. It is not yet known if combination chemotherapy is more effective with or without rituximab for non-Hodgkin's lymphoma.

PURPOSE: Randomized phase III trial to compare the effectiveness of combination chemotherapy with or without rituximab in treating older patients who have non-Hodgkin's lymphoma.

OBJECTIVES: I. Compare the efficacy of CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) with or without rituximab in older patients with diffuse mixed, diffuse large, or immunoblastic large cell non-Hodgkin's lymphoma of B-cell lineage with respect to the response rate, time to treatment failure, toxicity, and survival. II. Compare the efficacy of maintenance therapy consisting of rituximab vs observation alone after initial therapy with respect to the time to treatment failure, duration of response, toxicity, and survival of this patient population. III. Determine if maintenance therapy with rituximab results in the conversion of any partial response to complete response.

OUTLINE: This is a randomized study. For the first randomization, patients are stratified according to the number of risk factors (0-1 vs 2-4). For the second randomization, in addition to the number of risk factors, patients are stratified according to objective response to initial induction therapy (partial response vs complete response) and induction therapy (CHOP vs CHOP and rituximab). Patients are randomized to one of two treatment arms. Arm I: Patients receive CHOP chemotherapy comprising cyclophosphamide IV, doxorubicin IV, and vincristine IV on day 1 and oral prednisone on days 1-5. Treatment repeats every 21 days in the absence of unacceptable toxicity. Arm II: Patients receive treatment as in arm I. Patients also receive rituximab IV on days -7,-3, 41, and 83. Patients who achieve complete response (CR) after 4 courses of CHOP and remain in CR after 6 courses of CHOP are further randomized to one of two arms. Arm I (Maintenance therapy): Patients receive rituximab IV weekly for 4 weeks. Courses repeat every 6 months for 2 years in the absence of unacceptable toxicity. Arm II: Patients are observed. Patients who achieve partial response (PR) after 6 courses OR PR after 4 courses and then CR after 6 courses receive 2 additional courses of CHOP therapy. Patients are then also randomized to receive either maintenance therapy or observation as above. Patients with stable disease or disease progression are removed from the study. Patients are followed every 3 months for 2 years, every 6 months for 3 years, and then annually thereafter.

PROJECTED ACCRUAL: Approximately 630 patients will be accrued for this study within 4 years.

DISEASE CHARACTERISTICS: Histologically proven intermediate or high grade B-cell non-Hodgkin's lymphoma (other than Burkitt's, non-Burkitt's, undifferentiated, or lymphoblastic lymphoma) B-cell non-Hodgkin's lymphoma positive for CD19 and/or CD20 by slide-based immunohistochemistry or flow cytometry No mantle cell or follicular lymphoma Measurable disease, defined by at least one of the following: Physical examination Radiographic findings of at least 2 dimensions Bidimensional measurable defect or mass measuring at least 2 cm in diameter on radionuclide or CT scan Enlarged spleen extending at least 2 cm below the costal margin provided that there is no other likely explanation besides lymphomatous involvement Enlarged liver extending at least 5 cm below the costal margin along with biopsy-proven lymphomatous hepatic involvement No history of transformed lymphoma No known posttransplantation lymphoproliferative disorder No CNS involvement CALGB patients 60-65 years of age must not be eligible for any other study of higher priority 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: See Disease Characteristics 60 and over Performance status: ECOG 0-3 Life expectancy: Not specified Hematopoietic: Absolute granulocyte count at least 1,500/mm3 (unless due to lymphoma) Platelet count greater than 100,000/mm3 (unless due to lymphoma) Hepatic: Bilirubin no greater than 3.0 mg/dL Renal: Creatinine less than 2.1 mg/dL OR Creatinine clearance at least 60 mL/min Cardiovascular: No active heart disease including congestive heart failure, myocardial infarction within the past 3 months, or symptomatic ventricular arrhythmia LVEF at least 45% if prior history of heart disease exists Other: HIV negative No other malignancy within the past 5 years except squamous cell or basal cell skin cancer or carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics No prior biologic response modifier therapy No prior immunotherapy No prior rituximab Chemotherapy: No prior cytotoxic chemotherapy No concurrent dexrazoxane Endocrine therapy: Prior corticosteroids allowed Radiotherapy: No prior radiotherapy No prior radioimmunotherapy Surgery: Not specified