9°Y-Ibritumomab tiuxetan, fludarabine, and TBI-based nonmyeloablative allogeneic transplantation conditioning for patients with persistent high-risk B-cell lymphoma.

ABSTRACT

Nonmyeloablative allogeneic transplantation (NMAT) infrequently cures active chemoresistant, bulky, or aggressive B-cell lymphoma (B-cell non-Hodgkin lymphoma [B-NHL]). We hypothesized that 9°Y-ibritumomab tiuxetan-based NMAT would facilitate early cytoreduction in such patients promoting improved long-term disease control by the allogeneic graft. Forty high-risk B-NHL patients with persistent disease received 0.4 mCi/kg (maximum, 32 mCi/kg) 9°Y-ibritumomab tiuxetan, fludarabine, and 2 Gy total body irradiation and matched-related (15) or unrelated (25) transplantation. Baseline features included median age, 58 years (range, 29-69 years); median prior regimens, 6 (range, 3-12); chemosensitive disease, 6 (15%); bulk > 5 cm, 17 (range, 5.2-18.6 cm, 43%); diffuse large B-cell lymphoma, 14 (35%); and comorbidity score > zero, 34 (85%). Early responses were observed in 24 (60%, 14 complete remission/complete remission unconfirmed, 10 partial response) patients, including 17 of 29 (59%) with chemotherapy-resistant disease and 10 (59%) with bulk > 5 cm. The estimated 30-month survival, progression-free survival, and nonrelapse mortality were 54.1%, 31.1%, and 15.9%, respectively. Early response, baseline platelet counts over 25 000/µL, indolent histology, and related donors were associated with improved survival. The addition of 9°Y-ibritumomab tiuxetan to NMAT is safe and yields early responses and prolonged disease control in some of the highest-risk B-NHL patients. This trial was registered at www.clinicaltrials.gov as #NCT00119392.