Low rates of acute and chronic GVHD with ATG and PTCy in matched and mismatched unrelated donor peripheral blood stem cell transplants.

Introduction: We evaluated the combination of ATG and PTCy for GVHD prophylaxis in matched and mismatched unrelated PBSCTs for high-risk hematological malignancies.

Methods: We treated 102 patients with reduced intensity conditioning (RIC) with fludarabine, busulfan, and TBI 200 cGy. GVHD prophylaxis included rabbit ATG (thymoglobulin at total dose of 4.5 mg/kg divided over days -3 to -1), PTCy (50 mg/kg/day on day +3 and on day +4), and cyclosporine. Clinical and outcome data were collected retrospectively.

Results: Among 102 patients, 76 patients received 10/10 MUD transplants and 26 patients received 9/10 mismatched transplants. The median age was 59 years. At a median follow-up of 15 months (range 0.6 to -33 months), the 1-year OS in MUD and MMUD cohort was 75% and 50%, respectively (P = 0.027). The corresponding one-year PFS was 67% and 35%, respectively (P = 0.0024). The incidence of grade 3-4 acute GVHD was 11.8% in MUD and 3.8% in MMUD group, and that of NIH stage moderate/severe chronic GVHD in the 2 groups was 10.5% and 7.6%, respectively. Cytomegalovirus (CMV) reactivation was seen in 49% patients. The cumulative incidence of relapse was 21.1% in the MUD group and 42.3% in the MMUD group.

Conclusion: Our experience shows that PTCy and ATG can be combined for GVHD prophylaxis in matched unrelated donor PBSCTs with low rates of Gr3-4 acute GVHD and chronic GVHD, and acceptable relapse rates.