DISEASE CHARACTERISTICS:

• Histologically* confirmed follicular non-Hodgkin's lymphoma

  • Grade 1, 2, or 3a disease (> 15 centroblasts per high-power field with centrocytes present) NOTE: *Bone marrow biopsy as the sole means of diagnosis is not acceptable; fine-needle aspirates are not acceptable
• Confirmed CD20 antigen expression by flow cytometry or immunohistochemistry

• Measurable disease > 1 cm

  • No non-measurable disease only, including any of the following:

    • Bone lesions
    • Ascites
    • Pleural/pericardial effusion
    • Lymphangitis cutis/pulmonis
    • Bone marrow involvement

• Must have been treated with rituximab either alone or in combination with chemotherapy

  • Time to disease progression ≥ 6 months after last rituximab dose
  • Last prior treatment regimen need not include rituximab
• No known CNS involvement

PATIENT CHARACTERISTICS:

Performance status

• ECOG 0-2

Life expectancy

• Not specified

Hematopoietic

• Absolute neutrophil count ≥ 1,000/mm^3
• Platelet count ≥ 75,000/mm^3

Hepatic

• Bilirubin ≤ 2 times upper limit of normal (ULN) (unless due to Gilbert's disease or lymphoma)

Renal

• Creatinine < 1.5 times ULN (unless due to lymphoma) OR creatinine clearance > 30 mL/minute (patients on dialysis not allowed)

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No known HIV positivity

• No "currently active" secondary malignancy (e.g., Waldenstrom's macroglobulinemia) except nonmelanoma skin cancer

  • Patients are not considered to have a "currently active" second malignancy if they have completed anticancer therapy and are deemed to have < 30% risk of relapse by their physician
• No deep vein thrombosis or pulmonary embolism within the past 3 months

PRIOR CONCURRENT THERAPY:

Biologic therapy

• See Disease Characteristics
• See Radiotherapy

Chemotherapy

• See Disease Characteristics
• No concurrent chemotherapy

Endocrine therapy

• More than 2 weeks since prior corticosteroids except for maintenance therapy (at a dose ≤ 20 mg/day) for a nonmalignant disease

• No concurrent hormonal therapy except for the following:

  • Steroids for adrenal failure
  • Hormones for non-disease-related conditions (e.g., insulin for diabetes)

• No concurrent dexamethasone or other steroids as antiemetics

  • Concurrent dexamethasone for infusion reactions allowed

Radiotherapy

• No radioimmunotherapy within 12 months of study entry

Other

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