• Progression-free survival at 2 years [ Designated as safety issue: No ]
  
• Response rate after study completion [ Designated as safety issue: No ]
  

• Progression-free survival of subgroup at 2 years [ Designated as safety issue: No ]
  

OBJECTIVES:

• Determine the 2-year progression-free survival of older patients with previously untreated bulky stage II or stage III or IV diffuse large B-cell non-Hodgkin's lymphoma treated with iodine I 131 tositumomab in combination with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone.
• Determine the response rate (partial response, complete unconfirmed response, and complete response) in patients treated with this regimen.
• Determine the 2-year progression-free survival and response rate (partial response, complete unconfirmed response, and complete response) in BCL-2 positive patients treated with this regimen.

OUTLINE: This is a multicenter study.

• Rituximab and chemotherapy: Patients receive R-CHOP comprising rituximab IV over 6 hours; cyclophosphamide IV over 15-45 minutes; doxorubicin IV over 5-20 minutes; and vincristine IV over 5-15 minutes on day 1 and oral prednisone on days 1-5. Treatment repeats every 21 days for up to 6 courses in the absence of disease progression or unacceptable toxicity. Patients then undergo a restaging evaluation. Patients without progressive disease receive CHOP chemotherapy comprising cyclophosphamide, doxorubicin, vincristine, and prednisone as outlined above. Treatment with CHOP chemotherapy repeats every 21 days for 2 courses.
• Radiolabeled monoclonal antibody therapy: Approximately 4-8 weeks after completion of chemotherapy, patients receive tositumomab IV over 1 hour followed by a dosimetric dose of iodine I 131 tositumomab IV over 20 minutes. Patients then undergo gamma scans over a 1-week period in order to determine the correct treatment dose of iodine I 131 tositumomab. No more than 2 weeks after administration of the dosimetric dose, patients receive tositumomab IV over 1 hour followed by a treatment dose of iodine I 131 tositumomab IV over 20 minutes.

After completion of study treatment, patients are followed periodically for up to 5 years.

PROJECTED ACCRUAL: A total of 80 patients will be accrued for this study within 15 months.

DISEASE CHARACTERISTICS:

• Diagnosis of diffuse large B-cell non-Hodgkin's lymphoma, meeting 1 of the following stage criteria:

  • Bulky stage II disease
  • Stage III disease
  • Stage IV disease
• Confirmed CD20 antigen-positive disease
• Bidimensionally measurable disease
• Less than 20,000/mcL circulating lymphoid cells on WBC differential count

• Adequate sections AND a paraffin block OR ≥ 10 unstained sections from the original diagnostic specimen available

  • Needle aspiration or cytology are not considered adequate
• No clinical evidence of CNS involvement by lymphoma

• No prior diagnosis of indolent lymphoma

  • No histologic transformation

PATIENT CHARACTERISTICS:

Performance status

• Zubrod 0-2

Life expectancy

• Not specified

Hematopoietic

• See Disease Characteristics

Hepatic

• Not specified

Renal

• Not specified

Cardiovascular

• Ejection fraction ≥ 45% by MUGA OR
• No significant abnormalities by echocardiogram

Pulmonary

• No requirement for continuous supplemental oxygen

Other

• Fertile patients must use effective contraception during and for 6 months after completion of study treatment
• No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, stage I or II cancer in complete remission, or carcinoma in situ of the cervix
• No known HIV positivity

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No prior antibody therapy for lymphoma

Chemotherapy

• No prior chemotherapy for lymphoma

Endocrine therapy

• Not specified

Radiotherapy

• No prior radiotherapy for lymphoma

Surgery

• No prior solid organ transplantation

Other

• Concurrent enrollment on protocol SWOG-8947 (lymphoma serum repository) or protocol SWOG-8819 (lymphoma tissue repository) is encouraged