Monoclonal Antibody Therapy or Biological Therapy in Treating Patients With Chronic Lymphocytic Leukemia or Multiple Myeloma in Remission After Chemotherapy

RATIONALE: Monoclonal antibodies such as rituximab can locate tumor cells and either kill them or deliver tumor-killing substances to them without harming normal cells. Biological therapies such as interferon alfa-2b use different ways to stimulate the immune system and stop cancer cells from growing. PURPOSE: Phase II trial to study the effectiveness of rituximab or interferon alfa-2b in treating patients who have chronic lymphocytic leukemia or multiple myeloma in remission.