Outcomes of adults older than 70 years of age undergoing allogeneic stem cell transplantation.

We compared outcomes of patients ≥ 70 years old undergoing allogeneic stem cell transplantation (alloSCT) with graft-vs-host disease (GvHD) prophylaxis regimens either including post-transplant cyclophosphamide (PTCy) or without cyclophosphamide (non-Cy). The primary endpoint was GvHD-free, relapse-free survival (GRFS) at one and five years; secondary endpoints included clinically significant acute (grade III-IV) and chronic (extensive) GvHD, relapse, overall survival (OS), and non-relapse mortality (NRM). Among 61 patients, 41 received PTCy and 20 received non-Cy prophylaxis. Unrelated donors accounted for 80 % of allografts; all non-Cy patients had 10/10 HLA matches, while PTCy patients had 64 % matched, 29 % haploidentical, and 7 % mismatched unrelated donors. Acute GvHD occurred in 5 % of PTCy vs 15 % of non-Cy patients (p = ns). One-year chronic GvHD incidence was lower with PTCy (12 % vs 30 %, p = 0.03). One-year GRFS was similar (34 % PTCy, 35 % non-Cy; p = ns). At five years, OS was 20 % vs 30 % and GRFS 21 % vs 15 % for PTCy and non-Cy, respectively (p = ns). We observed similar outcomes among patients receiving GvHD prophylaxis with PTCy compared to non-Cy. Importantly, non-Cy patients had HLA-matched donors, whereas mismatched donors were possible for the PTCy group. In this way, PTCy seems to have equalized outcomes for fully matched and mismatched alloSCT by yielding similar one and five-year GRFS. We also found no significant difference in relapse rate, NRM, OS, and five-year GRFS between patients aged 70-74 and ages 75 + , showing that numerical age should not be a contraindication to alloSCT.