Monoclonal Antibody Therapy in Relapsed Non-Hodgkin's After Chemotherapy and Autologous Stem Cell Transplantation

Inclusion Criteria: * Diagnosis of relapsed B-cell non-Hodgkin's lymphoma (NHL) after high-dose chemotherapy and autologous stem cell transplantation * Less than 25% bone marrow involvement with NHL as evidenced by unilateral or bilateral biopsy within the past 6 weeks o Bone marrow biopsy should demonstrate 15-20% of cellular space occupied by normal hematopoiesis * CD20 antigen expression in tumor tissue within the past year as evidenced by 1 of the following: * Immunoperoxidase stains of tissue showing positive reactivity with L26 antibody * Flow cytometry studies * Measurable disease o More than 2 cm bidimensionally * 19 years of age and over * Performance status WHO 0-2 * Life expectancy at least 3 months * Absolute neutrophil count greater than 1,500/mm\^3 * Platelet count greater than 150,000/mm\^3 * Bilirubin less than 2.0 mg/dL * SGOT or SGPT no greater than 2.5 times upper limit of normal (unless due to lymphomatous infiltration of the liver) * Creatinine less than 2.0 mg/dL * Fertile patients must use effective contraception during and for 6 months after study therapy * HIV negative * At least 4 weeks since prior growth factors * At least 4 weeks since prior biologic therapy * At least 4 weeks since any prior cytotoxic chemotherapy (6 weeks for nitrosoureas) * At least 4 weeks since prior radiotherapy * Recovered from all prior therapy * At least 4 weeks since prior immunosuppressants Exclusion Criteria: * No active CNS lymphoma * No HIV- or AIDS-related lymphoma * No transfusion dependency * No active obstructive hydronephrosis * Not pregnant or nursing/negative pregnancy test * No active infection requiring oral or IV antibiotics * No human antimurine antibody positivity * No other major medical problems * No dependency on hematopoietic growth factors (e.g., epoetin alfa, interleukin-11, filgrastim \[G-CSF\], or sargramostim \[GM-CSF\]) * No prior radioimmunotherapy * No other concurrent biologic therapy of any kind * No prior fludarabine * No concurrent chemotherapy * No concurrent steroids except as maintenance for non-cancerous disease * No prior pelvic radiotherapy * No prior radiotherapy to more than 25% of estimated bone marrow reserve * No concurrent external beam radiotherapy * No other concurrent investigational drugs * No other concurrent anti-cancer therapy