Collection of Hematopoietic Stem Cells after Previous Radioimmunotherapy is Feasible and Does Not Impair Engraftment after Autologous Stem Cell Transplantation in Follicular Lymphoma

Major concerns about radioimmunotherapy (RIT) administration early in the course of follicular lymphoma (FL) are long-term toxicity and the theoretical impairment of hematopoietic stem cell (HSC) harvest, but few data are available about mobilization rates after RIT. This study evaluates the impact of prior therapy with RIT (yttrium-90 ibritumomab tiuxetan) and different chemotherapy regimens in all FL patients (N = 103) attempting HSC mobilization at our institution over the last 7 years. Sixty-nine patients received R-CHOP (rituximab-cyclophosphamide-doxorubicin-vincristine-prednisone) or CHOP-like regimens, 21 patients received R-FM (rituximab-fludarabine-mitoxantrone), and 13 patients received RIT before HSC mobilization. Median CD34+ cell yield at first mobilization was 7.2 × 106/kg in the R-CHOP group versus 4.3 in the R-FM group versus 1.7 in the RIT group (P = .02 R-CHOP versus R-FM; P < .0001 R-CHOP versus RIT; P < .02 R-FM versus RIT). Although 8 of 13 patients initially failed to collect enough HSC after RIT, a second and/or salvage harvest was successfully performed in 7 patients, with 10 of 13 patients (77%) finally undergoing autologous stem cell transplantation (ASCT). No differences in engraftment kinetics were observed between the three groups (R-CHOP versus R-FM versus RIT). Although mobilization was significantly impaired in patients previously treated with RIT, a salvage HSC harvest and ASCT after RIT were safe and feasible in most patients.