Rituximab, Yttrium Y 90 Ibritumomab Tiuxetan, Melphalan, and Autologous Peripheral Stem Cell Transplant in Treating Patients With Previously Treated Multiple Myeloma

OBJECTIVES:

Primary

- Determine the safety of rituximab, yttrium Y 90 ibritumomab tiuxetan, high-dose
melphalan, and autologous peripheral blood stem cell transplantation in patients with
previously treated multiple myeloma.

- Determine the effect of rituximab and yttrium Y 90 ibritumomab tiuxetan on the
clonotypic B-cells at baseline and at B-cell recovery in these patients.

Secondary

- Determine the response rate and progression factors (time to progression,
progression-free survival, and duration of response) in patients treated with this
regimen.

- Determine the effect of rituximab and yttrium Y 90 ibritumomab tiuxetan on the clonal
plasma cells in the blood and marrow prior to high-dose melphalan.

OUTLINE: This is a dose-escalation study of yttrium Y 90 ibritumomab tiuxetan.

Patients receive rituximab IV followed by a dosimetry dose of indium In 111 ibritumomab
tiuxetan IV over 10 minutes on day -22. Patients with acceptable biodistribution receive
rituximab IV followed by yttrium Y 90 ibritumomab tiuxetan IV over 10 minutes on day -14,
high-dose melphalan IV over 1 hour on days -2 and -1, and undergo autologous peripheral blood
stem cell transplantation on day 0. Patients also receive sargramostim (GM-CSF)
subcutaneously beginning on day 0 and continuing until blood counts recover.

Cohorts of 3-6 patients receive escalating doses of yttrium Y 90 ibritumomab tiuxetan until
the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that
at which 2 of 3 or 2 of 6 patients experience dose-limiting toxicity.

Bone marrow, blood, and urine samples are collected at baseline and then periodically during
study for biomarker correlative studies.

After completion of study treatment, patients are followed every 3 months for 5 years.

DISEASE CHARACTERISTICS:

- Diagnosis of multiple myeloma

- Previously treated disease

- Candidate for high-dose chemotherapy with melphalan and autologous stem cell
transplantation

- No definite evidence of myelodysplasia on pretreatment bone marrow by morphology or by
chromosome analysis (e.g., monosomy 7)

- Chromosome abnormalities from the myeloma clone allowed

PATIENT CHARACTERISTICS:

- ECOG performance status 0-2

- ANC ≥ 1,500/mm³

- Platelet count ≥ 100,000/mm³

- Bilirubin ≤ 2.0 mg/dL

- Alkaline phosphatase ≤ 3 times upper limit of normal (ULN)

- AST ≤ 3 times ULN

- Creatinine ≤ 2 times ULN

- LVEF ≥ 45%

- Corrected pulmonary diffusion capacity ≥ 50%

- No uncontrolled infection

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No other active malignancy (with the exception of nonmelanoma skin cancer) that
requires myelosuppressive chemotherapy or radiation therapy

- No HIV positivity

PRIOR CONCURRENT THERAPY:

- More than 3 weeks since prior myelosuppressive chemotherapy, except cyclophosphamide
pulsing for stem cell collection)

- No other concurrent immunotherapy, radiotherapy, chemotherapy or antimyeloma therapy

- Concurrent chronic corticosteroids at doses of prednisone ≤ 20 mg per day (or
equivalent) allowed

- Concurrent adjuvant hormonal therapy (e.g., tamoxifen citrate or leuprolide acetate)
allowed