Transplant Outcomes of 9/10 HLA Matched Unrelated Donors (MUD) Treated with Post-Transplant Cyclophosphamide for Prevention of Graft Versus Host Disease

Background:

Graft-versus-host disease (GVHD) is a major complication of allogeneic stem cell transplantation (ASCT). The incidence of GVHD with conventional GVHD prevention is higher with HLA mismatched compared to matched donors, with 69% of patients (pts) developing grade 2-4 and 16% grade 3-4 acute (aGVHD) and more than half the pts developing chronic (cGVHD), as previously reported by us(Ciurea SO abstract ASH 2010). Here we report preliminary results of 9/10 MUD transplant pts receiving GVHD prophylaxis with post-transplantation cyclophosphamide (PTCY), in addition to tacrolimus and mycophanolate mofetil (MMF).

Methods:

Patients were treated prospectively using a 9/10 MUD on a separate arm of a phase II clinical trial (2009-0266). Conditioning regimen consisted of Melphalan 140 mg/m2 on day −8 (100mg/m2 for pts ≥55 years or with comorbidities), Thiotepa 5-10 mg/kg on day −7 and Fludarabine 40 mg/m2/day on days −6, −5, −4, and −3. All patients received T-cell replete bone marrow graft. GVHD prophylaxis included PTCY 50mg/kg on days +3 and +4, MMF was given until day 100 and Tacrolimus until day 180 if no GVHD. Primary objectives were to determine the incidence of acute and chronic GVHD and non-relapse mortality (NRM), while secondary objectives included progression free survival (PFS) and overall survival (OS).

Results:

39 patients with median age of 50 years (range 20-64) received a 9/10 MUD with PTCY GVHD prophylaxis. 20 patients (51%) were women and AML/MDS was the most common indication for transplantation in 13(33%), NHL 8(21%), ALL 7(18%), AA in 4(10%) and CLL, CML/MPD, HL and MM constituted rest of the patients. Poor, intermediate and low risk cytogenetics were seen in 6, 8 and 4 patients with leukemia, respectively. 22 patients (56%) were not in complete remission at the time of transplantation. Median follow-up time for survivors was 35.9 months (range: 2.6–123.5). All patients engrafted the donor cells. Day 100 NRM for all pts was 18%.The cumulative incidence (CI) of grade II-IV aGVHD and gr III-IV aGVHD was 42% and 17%, respectively. CI of all cGVHD was only 20% and extensive only cGVHD was 13%. NRM for all pts was 36% at 1 year and 40% at 3 years. OS for all pts at 1 and 3 yr was 57% and 44%, while PFS at 1 and 3 yr was 43% and 39%, respectively.

Conclusions:

Post-transplant cyclophosphamide for prevention of GVHD which has been successfully used in haploidentical transplantation, resulted in a modest improvement in the rates of grade 2-3 and 3-4 acute GVHD compared to reports of standard GVHD prophylaxis for 9/10 MUD transplants. However, a promising low rate of chronic GVHD was observed. This approach can produce durable remissions for patients with hematologic malignancies who lack an HLA matched donor.

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