Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically proven relapsed or refractory, low-grade,
follicular, or transformed B-cell non-Hodgkin's lymphoma (NHL) Prior rituximab allowed if
no response achieved CD20-positive B-cells in lymph nodes or bone marrow required for
small lymphocytic or transformed NHL Less than 25% of bone marrow cellularity in lymphoma
cells No impaired bone marrow reserve, as indicated by one or more of the following: Prior
myeloablative therapy with bone marrow transplantation or peripheral blood stem cell
rescue Platelet count less than 100,000/mm3 Hypocellular bone marrow (no more than 15%
cellularity) Marked reduction in bone marrow precursors of one or more cell lines
(granulocytic, megakaryocytic, or erythroid) History of failed stem cell collection Not
eligible for any active ibritumomab tiuxetan investigative protocols No CNS lymphoma,
AIDS-related lymphoma, or chronic lymphocytic leukemia No pleural effusion 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: WHO 0-2 Life expectancy: At
least 3 months Hematopoietic: See Disease Characteristics Absolute neutrophil count at
least 1,500/mm3 Lymphocyte count no greater than 5,000/mm3 (for small lymphocytic
lymphoma) Platelet count at least 150,000/mm3 Hepatic: Bilirubin no greater than 2.0 mg/dL
Renal: Creatinine no greater than 2.0 mg/dL Other: Not pregnant or nursing Negative
pregnancy test Fertile patients must use effective contraception during and for 6 months
after study HIV negative No serious nonmalignant disease or infection that would preclude
study No antimurine antibody reactivity

PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics At least 6 weeks
since prior rituximab At least 3 weeks since prior immunotherapy and recovered No prior
radioimmunotherapy At least 2 weeks since prior filgrastim (G-CSF) or sargramostim
(GM-CSF) Chemotherapy: See Disease Characteristics At least 3 weeks since prior
chemotherapy (6 weeks for nitrosourea or mitomycin) and recovered Endocrine therapy: Not
specified Radiotherapy: See Biologic therapy At least 3 weeks since prior radiotherapy and
recovered No prior external beam radiotherapy to more than 25% of active bone marrow
(involved field or regional) Surgery: At least 4 weeks since prior major surgery (other
than diagnostic) and recovered Other: At least 3 weeks since prior anticancer therapy and
recovered At least 8 weeks since prior phase II drugs and recovered No other concurrent
myelosuppressive antineoplastic agents No other concurrent antineoplastic therapy