DISEASE CHARACTERISTICS:

• Histologically confirmed* de novo B-cell non-Hodgkin's lymphoma (NHL) of 1 of the following WHO histologic subtypes:

  • Diffuse large cell lymphoma, including any of the following morphologic variants:

    • Centroblastic
    • Immunoblastic
    • T-cell/histiocyte rich
    • Anaplastic
  • Mediastinal (thymic) large cell lymphoma
  • Intravascular large cell lymphoma NOTE: *Fine needle aspirates or core biopsies must not be the only diagnostic material
• Stage I primary mediastinal (thymic) OR stage II-IV disease
• CD20-positive disease
• No underlying low-grade lymphoma (e.g., transformed lymphoma or low-grade lymphoma in the bone marrow)

• No known lymphomatous CNS involvement

  • Lumbar puncture required unless there are no neurological symptoms NOTE: 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

• 18 and over

Performance status

• ECOG 0-2

Life expectancy

• Not specified

Hematopoietic

• Absolute neutrophil count ≥ 1,000/mm^3^*
• Platelet count ≥ 100,000/mm^3^*
• No active bleeding unrelated to NHL NOTE: *Unless due to NHL

Hepatic

• Bilirubin ≤ 2 mg/dL* NOTE: *Unless due to NHL or Gilbert's disease

Renal

• Creatinine ≤ 1.5 mg/dL^* OR
• Creatinine clearance ≥ 50 mL/min^* NOTE: *Unless due to NHL

Cardiovascular

• No active ischemic heart disease
• No congestive heart failure

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• HIV negative
• No active uncontrolled bacterial or viral infection unrelated to NHL
• No other active medical process unrelated to NHL

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No prior rituximab

Chemotherapy

• No prior chemotherapy for other malignancies
• No prior cytotoxic chemotherapy
• No other concurrent chemotherapy

Endocrine therapy

• Prior short course (< 10 days) glucocorticoids allowed for an urgent local disease complication (e.g., cord compression or superior vena cava syndrome) at diagnosis
• No concurrent hormonal therapy except steroids for adrenal failure or hormones for non-disease related conditions (e.g., insulin for diabetes)
• No concurrent dexamethasone or other steroidal antiemetics

Radiotherapy

• Prior limited field radiotherapy allowed for an urgent local disease complication (e.g., cord compression or superior vena cava syndrome) at diagnosis
• No concurrent radiotherapy except for isolated CNS lesions

Surgery

• Not specified

Other

• No other concurrent investigational or commercial agents or therapies for NHL