Rituximab and Denileukin Diftitox in Treating Patients With Previously Untreated Stage III or Stage IV Follicular B-Cell Non-Hodgkin's Lymphoma

RATIONALE: Monoclonal antibodies, such as rituximab, can block cancer growth in different ways. Some block the ability of cancer cells to grow and spread. Others find cancer cells and help kill them or carry cancer-killing substances to them. Combinations of biological substances in denileukin diftitox may be able to carry cancer-killing substances directly to cancer cells. Giving rituximab together with denileukin diftitox may kill more cancer cells. PURPOSE: This phase II trial is studying how well giving rituximab together with denileukin diftitox works in treating patients with previously untreated stage III or stage IV follicular B-cell non-Hodgkin's lymphoma.

OBJECTIVES: Primary * Determine the response rate (complete response \[CR\], unconfirmed CR, and partial response) in patients with previously untreated stage III or IV follicular B-cell non-Hodgkin's lymphoma treated with rituximab and denileukin diftitox. * Assess the overall survival, time-to-progression, duration of response, and time-to-new therapy in patients treated with this regimen. Secondary * Determine whether this regimen depletes or inhibits the function of regulatory T cells in these patients. OUTLINE: This is a multicenter study. Patients receive rituximab IV on days 1, 8, 15, and 22. Patients also receive denileukin diftitox IV over 15-60 minutes on days 1-5. Treatment with denileukin diftitox repeats every 21 days for up to 4 courses in the absence of disease progression or unacceptable toxicity. Blood is collected at baseline; on day 1 of courses 2-4; and 1 and 4 months after completion of study treatment for research studies. Research studies include analysis of peripheral blood lymphocyte subsets expressing CD3, CD4, CD8, CD19, CD25, and CD26 by flow cytometry; quantitation of CD4+, CD25+ regulatory T cells by flow cytometry; tumor-specific γ-interferon-secreting T cells by enzyme-linked immunospot assay; tumor-specific cytotoxic T-lymphocyte activity; and immune activation by enzyme-linked immunosorbent assay. After completion of study treatment, patients are followed periodically for up to 5 years after registration. PROJECTED ACCRUAL: A total of 53 patients will be accrued for this study.