Outcomes of primary graft failure in acute myeloid leukemia patients following unrelated transplantation with post-transplant cyclophosphamide: a study from the ALWP/EBMT.

We assessed pGF in 2497 AML patients undergoing HSCT from 8-10/10 HLA-matched UD with PTCy. pGF was defined as failure to achieve an ANC ≥ 0.5 × 10/L by day +30 after HSCT. The day +30 cumulative incidence of ANC was 92.6% (95%CI: 91.5-93.6), and the incidence of death without ANC recovery was 1.8% (95% CI: 1.3%-2.3%), corresponding to 141 (5.6%) patients not achieving an ANC ≥ 0.5 × 10/L by day +30. PB was the graft source in 89.4% of the patients, and 56% received reduced-intensity conditioning. 21 patients underwent a second HSCT (15 in the absence of ANC recovery and 6 after ANC recovery). 1-y NRM and RI post-pGF were 22.1% and 22.4%, respectively. 1-y LFS and OS post-pGF were 59% and 55.5%, respectively. ANC recovery evaluated as a time-dependent covariate, KPS ≥ 90, and being in CR at the time of HSCT were associated with improved OS. In conclusion, the incidence of pGF post-unrelated HSCT with PTCy was 5.6%. Of the patients who failed to engraft by day +30, 70.9% did so by day +60. A second transplant can save some of the patients with pGF.