Background: Radioimmunotherapy (RIT) is an effective treatment of Non-Hodgkin Lymphoma (NHL). Nonetheless, the use of RIT outside of clinical trials has been limited. We report here the experience in 25 patients treated with Y-90 ibritumomab tiuxetan off-protocol at a single institution.

Patients and Methods: The charts of all patients treated with RIT between October, 2004 and May, 2006 were retrospectively reviewed in accordance with Good Clinical Practice guidelines. 19 patients were treated with RIT alone while 6 were treated with RIT in combination with high-dose chemotherapy and autologous hematopoietic stem cell transplant (HSCT). Dosimetry was not performed.

Results: The median age of patients was 56 years (range 43–71 years). 13 of 25 had high-grade lymphoma (either transformed lymphoma or diffuse large B-cell lymphoma). The median IPI was 3. The median number of prior regimens was 3 (range 1–6). 6 patients had received fludarabine. 3 patients had undergone prior autologous HSCT and one had undergone allogeneic HSCT. The median time to platelet recovery >20 × 109/L was 35 days. One patient continues to have platelets <20 × 109/L 380 days post-RIT. The median time to recover platelets to >20 × 109/L was 72 among patients who had previously received fludarabine. Prior HSCT also appeared to be associated with prolonged thrombocytopenia. 7 patients remained neutropenic (ANC<0.5 × 109/L) for >30 days. One patient who had been treated with 4 lines of prior chemotherapy, including prolonged chlorambucil, developed acute myeloid leukemia at 6 months post-RIT. There have been 3 deaths to date, all due to disease progression at 1, 1, and 3 months post-RIT. The overall response rate in 21 of 25 patients was 84% with 9 patients achieving CR. With a median follow-up of 7 months, 5 patients have progressed.

Conclusion: The use of off-protocol RIT in our institution was associated with similar response rates to those reported in patients treated on-protocol. Off concern, however, is the significant hematologic toxicity. There was an association between prior fludarabine and prolonged thrombocytopenia that has not been reported previously.

Disclosures: Y-90 ibritumomab tiuxetan has been licenced for treatment of relapsed/refractory low-grade follicular or transformed B-cell NHL. In this case series 2 patients with relapsed diffuse large B-cell lymphoma were treated.; Ahmed Galal has received funding from Berlex Canada Inc. to conduct an investigator sponsored clinical trial.

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