BMT CTN 1703 findings show PTCy improves outcomes for older adults undergoing allogeneic HCT

January 2026

Although the median age at diagnosis for blood cancers is 70, only 15% of patients in that age group receive allogeneic hematopoietic cell transplant (alloHCT), a potentially curative treatment. Historically, concerns about post-transplant complications such as graft-versus-host disease (GVHD) have limited alloHCT use in older adults. The BMT CTN 1703 trial evaluated whether a GVHD prevention strategy using post-transplant cyclophosphamide (PTCy) could improve outcomes for this older population.

This analysis of the Phase III BMT CTN 1703 trial investigated a PTCy-based GVHD prophylaxis regimen in adults ≥70 years undergoing alloHCT with matched related or unrelated (MUD) donors after reduced-intensity conditioning (RIC). The goal was to determine whether the benefits of PTCy-based GVHD prophylaxis, including better GVHD control and improved immunosuppression-free survival, extended to adults ≥70 years.

In this study, 96 patients aged 70 or older with hematologic malignancies (AML, MDS and others) were randomized into 2 GVHD prophylaxis groups after undergoing RIC. The PTCy group received PTCy, mycophenolate mofetil and tacrolimus, and the Tac/MTX group received tacrolimus and methotrexate.

In both groups, most patients received grafts from an MUD, followed by grafts from matched related donors (MRD), and then mismatched unrelated donors (MMUD). The primary endpoint was 1-year GVHD-free, relapse-free survival (GRFS). Key secondary endpoints included chronic GVHD (cGVHD), GVHD-free survival, relapse/progression, relapse-free survival (RFS), non-relapse mortality (NRM) and overall survival (OS).

The study found that the PTCy group showed superior GRFS and OS at 1 year compared to the Tac/MTX group:

• Adjusted GRFS: PTCy 67.1% vs. Tac/MTX 29.5%, p=0.001
• Adjusted OS: PTCy 94.3% vs. Tac/MTX 60.2%, p=0.001

Cumulative chronic GVHD at 1 year did not differ between groups:

• PTCy: 23.5% (95%CI, 11.9-37.3)
• Tac/MTX: 30.5% (95% CI, 8.1-30.9)

PTCy recipients had significantly lower relapse/progression risk and NRM compared to Tac/MTX recipients:

• Relapse/progression risk: HR=0.30 (95%CI, 0.10-0.88)
• Cumulative incidence at 1 year: PTCy 14.3% (95%CI, 6.2-25.6) vs. Tac/MTX 29.3% (95%CI, 18.8-40.6)
• NRM: HR=0.19 (95%CI, 0.04-0.94), p=0.04
• RFS: HR=0.27 (95%CI, 0.12-0.64)
• Adjusted 1-year RFS: PTCy 80.5% (95%CI, 66.2-89.2) vs. Tac/MTX 50.3% (95%CI, 37.2-62.0)

Overall, patients in the PTCy group had a significantly higher probability of being alive, relapse-free and off immunosuppression at 1 year post-transplant.

The benefits of PTCy-based GVHD prophylaxis extended to adults ≥70 years, resulting in improved GVHD control and immunosuppression-free survival. Older patients receiving PTCy also experienced lower observed NRM and improved OS compared to patients receiving conventional GVHD prophylaxis. These findings support that older age alone should not be a barrier to alloHCT in the era of PTCy.

Abedin, et al., published in Blood Advances