Post-Transplant Cyclophosphamide (PT-Cy) Based Haploidentical Cell Transplantation (Haplo) Versus Rabbit Anti-Thymocyte Globulin (r-ATG) Based HLA Matched Unrelated Donor (MUD) Transplantation in Patients (pts) with Relapsed/Refractory Lymphoma

Background PT-Cy has emerged as an effective strategy for graft-versus-host disease (GVHD) prophylaxis in Haplo. The reported risk of GVHD with non-PT-Cy in pts receiving MUDs varies between centers. In this report, we compared the engraftment rates, survival, risk of GVHD and comorbidities between PT-Cy Haplo and r-ATG-based MUDs approach in pts with relapse/refractory lymphoma receiving an allogeneic transplantation. Method We retrospectively evaluated 160 adult pts with lymphoma who received Haplo (n=35) or r-ATG-MUDs (n=125) at our center between 2012 and 2018. Pts received GVHD prophylaxis of r-ATG (2-4 mg/kg total on days -3 to -1), tacrolimus and methotrexate if MUD, and tacrolimus and mycophenolate mofetil in addition to PT-Cy (50 mg/kg on days+3, +4) if Haplo. Tacrolimus taper was initiated at 6 months after transplantation in pts with no active GVHD. The study was IRB-approved. Results Haplo pts were more likely to be younger (median age 47 vs 55 yrs; P=0.032), have a lower HCT-Comorbidity Index (median 2 vs 3; P=0.048), and to include more diffuse large b-cell lymphoma (31% vs 22%, and Hodgkins disease (29% vs 16%) (P=0.015). Significant differences were also observed in the conditioning intensity and cell source of transplants between the 2 groups. The majority of Haplo pts (80%) received a reduced intensity-conditioning (RIC) of melphalan/fludarabine +/- 2Gy TBI; the remaining received a myeloablative (MA) busulfan-based regimen (9%) or nonmyeloablative (NMA) (11%) conditioning. In comparison, the percentage of MUDs pts receiving RIC, MA and NMA [bendamustine, fludarabine, rituximab or fludarabine, cyclophophamide, rituximab were 31%, 22% and 46%, respectively (P 500 (18 days vs 10 days; P 20k were 25.5 days vs 10 d