T‐cell–depleted haploidentical stem cell transplantation results improve with time in adults with acute leukemia: A study from the Acute Leukemia Working Party of the European Society of Blood and Marrow Transplantation (EBMT)

BACKGROUND T‐cell–depleted, haploidentical transplantations (haplos) are commonly offered to patients who have high‐risk, acute leukemia in the absence of a human leukocyte antigen (HLA) full‐matched donor. METHODS To determine the effect of transplantation period, the authors divided 308 adults with de novo, acute leukemia who underwent T‐cell–depleted haplo from 2005 to 2015 into 2 groups, according the year in which they underwent transplantation (2005‐2011 [n = 191] and 2012‐2015 [n = 117]). RESULTS The median age was 41 years in patients who underwent transplantation before 2012 and 46 years in those who underwent transplantation after 2012 (P = .04). Most patients had acute myeloid leukemia (75% vs 69%; P = .26) and were in first complete remission (CR1) (55% vs 64%; P = .12) at the time of transplantation. The cumulative incidence of grade 2, 3, and 4 acute graft‐versus‐host disease (GvHD) and chronic GvHD were not different between the 2 groups (acute GvHD: 20% vs 22% cumulative incidence in patients who underwent haplo before and after 2012, respectively [P = .67]; chronic GvHD: 19% vs 11% cumulative incidence, respectively; P = .12]. The 2‐year relapse incidence was 20%, the nonrelapse mortality (NRM) rate was 48%, and no difference was observed over time (21% vs 19% [P = .72] and 54% vs 38% [P = .11] for patients who underwent haplo before and after 2012, respectively). The main cause of NRM was infection. Haplo after 2012 (hazard ratio [HR], 0.57; P = .01), younger age (HR, 0.82; P = .02), and receipt of a reduced‐intensity conditioning (RIC) regimen (HR, 0.53; P = .01) were independently associated with lower NRM. The 2‐year overall survival rate was 36% and improved after 2012 (29% vs 47% before 2012; P = .02); and it was higher for patients who underwent transplantation in CR1 (41% vs 29%; P = .01). In multivariate analysis, haplo after 2012 (HR, 0.54; P = .003) and receipt of a RIC regimen (HR, 0.54; P = .005) were independently associated with better overall survival. Similarly, leukemia‐free survival and GvHD‐free/relapse‐free survival (GRFS) improved over time: the leukemia‐free survival rate was 31% (25% vs 43% in the groups who underwent transplantation before and after 2012, respectively; P = .05), and the GRFS rate was 24% (19% vs 34%, respectively; P = .09). In addition, leukemia‐free survival and GRFS improved among patients who received a RIC regimen. CONCLUSIONS The outcome of patients with acute leukemia who underwent T‐cell–dep