EBMT 2019 | Graft-versus-host disease prophylaxis with reduced intensity conditioning regimen combined with anti-thymocyte globulin and post-transplantation cyclophosphamide for AML

Reduced-intensity conditioning (RIC) for allogeneic stem cell transplantation is known to induce graft-versus-host disease (GvHD) and thereby increase non-relapse mortality (NRM). Immunosuppressive therapies to reduce the risk of GvHD may often come at the price of higher relapse rates. Therefore, new strategies to reduce GvHD while maintaining low relapse rates are needed.

On Tuesday 26 March 2019, Oral Session 03 (OS03) took place at the 45th Annual Meeting of the European Society of Blood and Marrow Transplantation (EBMT), Frankfurt, DE. During that session, Abstract OS03-2 was presented by Maria Queralt Salas from Princess Margaret Cancer Centre, Hans Messner Allogeneic BMT Program, Toronto, Canada.

The primary objective of the study was to assess the safety and efficacy of reducing the intensity conditioning regimen (RIC) combined with anti-thymocyte globulin (ATG), as well as post-transplant cyclophosphamide (PTCy) for graft-versus-host disease (G_VHD) prophylaxis in patients diagnosed with acute myeloid leukemia (AML).

Patient and methods

• N = 104
• Median follow up: 19 months: (5-35 months)
• Patients received the following RIC regimen:
• Fludarabine (30mg/m²/day day -5 to -2)
• Busulfan (3.2kg/m²/day, day -3 and -2)
• Total body irradiation (200 cGy) (day -1)
• ATG (4.5 mg/kg administered over 3 days, day -3 to -1)
• PTCy (50mg/kg/day: day +3 and, +4)
• cyclosporine (2.5 mg/kg iv from day +5 onward)
• Un-manipulated peripheral blood stem cells (PBSC) were infused

Table 1: Summary of patients and methods

Key findings

• One year overall survival (OS): 67.7% (95% CI 58.6-76.8)
• Progression-free survival (PFS): 60.8% (95% CI 51.1-70.5)
• Non-relapse mortality (NRM): 16.4% (95% CI 6.9-25.8)

The study identified that the main causes of death were:

• Relapse (18%)
• Infection (13%)

The key findings can be found summarized in Table 2 and Table 3.

Table 2: Key findings

Table 3: Univariate analysis *RFS (Relapse-free survival)

Conclusion

Dr. Queralt Salas concluded that the combination therapy, RIC with ATG and PTCy provided a very low rate of both aGvHD and cGvHD, as well as an adequate relapse rate. The univariant analysis identified that OS and RFS were not significantly affected by donor type or cytogenetic risk type. However, KPS <80% and not achieving CR before the transplant was associated with a significantly lower OS and RFS. Dr. Queralt Salas ended the session by emphasizing that this protocol gives enough graft-versus-leukemia effect in those patients who have high-risk leukemia, however, patients with active disease at the time of transplant may not benefit from this protocol.