Tositumomab and Iodine I 131 Tositumomab in Treating Patients With Chronic Lymphocytic Leukemia or Small Lymphocytic Lymphoma in First Remission

PRIMARY OBJECTIVES: I. To estimate the progression-free survival at 2 years following administration of 131I-tositumomab (tositumomab and iodine I 131 tositumomab) in patients with CLL/SLL who achieve a complete remission (CR) or partial remission (PR) with prior therapy. II. To improve the response rate by administering 131I-tositumomab to patients who have achieved a PR not a CR after any prior therapy. III. To eliminate residual disease (documented by flow cytometry or polymerase chain reaction \[PCR\]) using 131I-tositumomab in patients who have achieved a CR after any prior therapy. SECONDARY OBJECTIVES: I. To evaluate the toxicities of 131I-tositumomab in 1st remission patients with previously treated CLL/SLL. OUTLINE: Patients receive tositumomab and iodine I 131 tositumomab intravenously (IV) over 90 minutes on day 0 and then again 7-14 days later over 30-60 minutes. After completion of study treatment, patients are followed up weekly for 3 months, every 3 months for 2 years, every 6 months for 3 years, and then annually thereafter.