Phase I trial of (90)Y-ibritumomab tiuxetan in patients with relapsed B-cell non-Hodgkin's lymphoma following high-dose chemotherapy and autologous stem cell transplantation.

Between January 2001 and September 2005, 19 patients with progressive B-cell non-Hodgkin's lymphoma were treated with a cohort-specific dose of yttrium-90 ibritumomab tiuxetan (0.10 - 0.20 mCi/kg) to determine appropriate dosing in patients who had previously received high-dose chemotherapy and autologous stem cell transplantation (ASCT). Patients were required to have adequate end organ function and bone marrow status. Patients had been treated with a median of three prior therapies (range, 1 - 9). The median time from ASCT to radioimmunotherapy was 28 months. Hematologic toxicities were dose-limiting and included grade 3 - 4 thrombocytopenia (53%), neutropenia (32%), and anemia (21%). The majority of grade 3 - 4 events occurred at the 0.2 mCi/kg dose level. Nine patients responded (complete response, complete response unconfirmed, or partial response) to the therapy. At a median follow-up of 37 months, the 1-year event-free and overall survival rates were 26% and 57%, respectively. A dose of 0.2 mCi/kg ibritumomab tiuxetan is safe and effective for patients with progressive disease after high-dose chemotherapy and ASCT.