Immunotherapy with rituximab during peripheral blood stem cell transplantation for non-Hodgkin's lymphoma

Peripheral blood stem cell grafts from patients with lymphoma are often con taminated with neoplastic cells. Administration of a lymphoma-specific mono clonal antibody before collecting stem cells may be one way of reducing the contamination. Similarly, an antibody after transplantation at a time of m inimal residual disease may increase the efficacy of the procedure. The obj ective of this study was to determine the safety of using rituximab as both an in vivo purging agent and a posttransplantation adjuvant. Eligible pati ents with lymphoma received 375 mg/m(2) rituximab intravenously (IV) on day 1, 2.5 g/m(2) cyclophosphamide TV on day 4, and 10 mug/kg per day filgrast im star-ring on day 5 and continuing until completion of leukapheresis. Pat ients subsequently received a standard preparative regimen and then receive d 375 mg/m2 rituximab TV 7 days after platelet independence was achieved. T wenty-five patients (14 men, 11 women; median age, 51 years) were enrolled. Of the 25 patients, 23 received transplants after at least 2.0 x 10(6) CD3 4(+) cells/kg were harvested. As determined with a sensitive polymerase cha in reaction assay 6 of 7 stem cell products tested were free of tumor conta mination. All patients engrafted promptly and the rituximab infusions were well tolerated. Transient neutropenia of uncertain etiology occurred in 6 p atients a median of 99.5 days posttransplantation. An additional patient de veloped progressive pancytopenia. Rituximab used as an in vivo purging agen t and adjuvant immunotherapy with peripheral blood stem cell transplantatio n for non-Hodgkin's lymphoma is a well-tolerated regimen. However, the ulti mate determination of efficacy will require the results of ongoing studies.