Successful PBSC Mobilization, Collection, Transplantation and Engraftment after Radioimmunotherapy with Yttrium-90 Ibritumomab Tiuxetan for Non-Hodgkin’s Lymphoma (NHL).

Radioimmunotherapy (RIT) is a useful addition to the armamentarium against NHL. Due to concerns about chronic myelosuppression and the possible inability to mobilize stem cells or tolerate further therapy after RIT, this modality has not been commonly utilized in potential transplant candidates. We report the successful mobilization, collection, transplantation and engraftment of 5 patients with NHL following yttrium-90 ibritumomab tiuxetan. Patients had follicular lymphoma, grade I or II (n=3), transformed follicular lymphoma (n=1) or blastic variant mantle cell lymphoma (n=1). Time from RIT to mobilization was 10 months (median; range 7–27 months). The median number of regimens prior to RIT was 2.5 (range 1–4) including prior autologous transplant (n=1). The median number of regimens following RIT and prior to transplant was 1.5 (range 1–2). All patients exhibited chemosensitive disease. Patients were mobilized with R-ICE/G-CSF (n=4) or G-CSF alone (n=1) and required 2.8 leukaphereses (mean; range 2–5). The CD34 yield was 3.8x10⁶ CD34+ cells/kg (median; range 3.4–5.1x10⁶ CD34+ cells/kg). All patients received busulfan, VP-16, ARA-C and cyclophosphamide (BVAC) as the preparatory regimen. One patient received IL-2 from day 0 to day 11. Time to engraftment was 13 days (median; range 9–19 days) for an absolute neutrophil count (ANC) >500 cells/ml and 23 days (median; range 15–44 days) for a platelet count>20x10³/ml. The patient on the IL-2 study showed delayed engraftment of both ANC (day 19) and platelets (day 27). The patient with mantle cell lymphoma, who was undergoing his second autologous transplant, exhibited delayed platelet engraftment (day 44). Time to engraftment did not differ significantly for either ANC (p=0.16) or platelets (p=0.10) in 18 RIT-naïve NHL patients receiving BVAC and an autologous peripheral blood stem cell transplant (PBSC) during the same time period. There were no treatment-related deaths. With a median follow up of 12 months, one patient has died of disease recurrence. Two patients remain in complete remission. Two patients are alive with disease (relapse at 12 months and 14 months) and are currently receiving therapy. No patient has demonstrated laboratory or cytogenetic evidence of a myelodysplastic syndrome. In conclusion, heavily pretreated patients who have received radioimmunotherapy with yttrium-90 ibritumomab tiuxetan and subsequently relapse can successfully undergo mobilization, collection, and autologous PBSC transplant. These patients demonstrate full engraftment, durable remissions and tolerate additional therapy should relapse occur following transplant.