medwireNews: Preliminary results indicate that a chemotherapy-free regimen may offer favorable outcomes for patients with high-risk acute myeloid leukemia (AML) undergoing allogeneic hematopoietic transplantation (alloHCT).

The research was presented at the virtual 62nd American Society of Hematology Annual Meeting and Exposition by Anthony Stein, from the Gehr Family Center for Leukemia Research at City of Hope in Duarte, California, USA.

The study included 18 AML patients aged 16–60 years who had achieved a first or second complete response (CR) without minimal residual disease and were undergoing alloHCT with an HLA-identical sibling donor (44.4%) or a 10/10 allele-matched unrelated donor (55.6%). 

All but one of the patients met the intermediate (50.0%) or unfavorable (44.4%) European Leukemia Network criteria for cytogenetic risk, the presenter noted.

Over the 4 days before bone marrow or peripheral blood stem cell infusion, patients were given up to 20 Gy of total marrow and lymphoid radiation targeted at the skeleton, major lymph node chains, testes, spleen, ribs, sternum, and skull, with 12 Gy aimed at the liver and brain, and lower doses to non-target regions, such as the heart and lungs.

On days 3 and 4 after transplantation, the patients were given cyclophosphamide 50 mg/kg followed by initiation of tacrolimus and G-CSF on day 5 for at least 90 days, and follow-up for a median 12.5 months.

All patients engrafted, with neutrophil and platelet recovery reported after a median 14 and 20 days, respectively.

The primary endpoint of survival free from graft-versus-host disease (GvHD) or relapse (GRFS) was achieved by 60.6% of patients at 12 months and 40.4% at 24 months, Stein reported.

Overall survival was 100% at 12 months and 85.7% after 24 months, with leukemia-free survival rates at both these time points of 83.0%.

Over the first 100 days, acute GvHD occurred at grade II–IV in 11.1% of patients and at grade III–IV in 5.6%. Chronic GvHD was reported in 29.1% at 12 months and 42.5% at 24 months, with 16.6% having experienced moderate or severe chronic GvHD by 24 months.

One patient died from progressive disease and one patient developed chronic GvHD around 1.75 years after transplantation but was improving on treatment with prednisone, tacrolimus, and ruxolitinib, Stein said.

Bearman toxicity scores showed three cases of grade 2 bladder toxicity and one case of grade 2 stomatitis but no grade 3–4 events or toxicity-related mortality.

“This chemotherapy-free conditioning regimen, together with cyclophosphamide and tacrolimus, is safe and feasible, with no non-relapse mortality,” Stein summarized.

He continued: “Almost all participants with greater than 1 years’ follow-up have discontinued immunosuppressive therapy, reducing financial burden and leading to improved quality of life.”

Noting that the “preliminary results suggest an improved GRFS rate,” he concluded that “a larger phase 2 trial is in preparation to corroborate these data.”

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62nd ASH Annual Meeting and Exposition; 5–8 December 2020