Post-Transplant Cyclophosphamide Following a Myeloablative Conditioning For Hematologic Malignancies Receiving An Unmanipulated Haploidentical Bone Marrow Transplant

Unmanipulated family haploidentical transplants are becoming increasingly used in patients lacking an HLA identical family donor, or a well matched unrelated donor.

This is an updated analysis of our program of haploidentical bone marrow transplant (hBMT) , followed by post-transplant high dose cyclophosphamide (PT-CY) in 95 patients with hematoloigic malignancies receiving a myeloablative conditioning.

The conditioning regimen consisted of thiotepa, busulfan, fludarabine (TBF) (n=47) , thiotepa melphalan fludarabine (n=5) , or 9.9-12 Gy TBI + fludarabine (n=43). The patients’ median age was 49 years (17-74); the disease status at the time of transplant, was first complete remission (CR1, n=29) , CR2 (n=23), or active disease (n=38,40%). The diagnosis was AML (35%), ALL (24%), MDS (12%) myeloproliferative disorders (12%), other malignancies (17%). The total nucleated cell dose infused was 3.37 (1.4-9.17). The median follow up for surviving patients is 440 days (90-930). Graft versus host disease (GvHD) prophylaxis consisted in PT-CY on day+3 and +5 , cyclosporine (from day 0) , and mycophenolate (from day +1).

The cumulative incidence of neutrophil (PMN) engraftment was (90%) and all surviving patients on day +30 had full donor chimerism. The median day for neutrophil engraftment was day +17 (11-32). The cumulative incidence (CI) of grade II-III acute GvHD was 14%, and of moderate chronic GvHD 8%, severe cGvHD 9%. The CI of transplant related mortality (TRM) is respectively 7%, 17%, 26% for patients in CR1, CR2, or with active disease. The CI of relapse is respectively 17%, 30%, 37% for patients in CR1, CR2, or with active disease. The overall actuarial survival is respectively 75%, 44%, 32% for patients in CR1, CR2, or with active disease (p=0.002) (Fig.1). The most frequent cause of death was leukemia (26%) followed by infections (9%).

These data confirm our first report on 50 patients and support the use of myeloablative conditioning regimens, followed by h-BMT with PT-CY. The risk of acute and chronic GvHD seems relatively low , as well as the overall transplant related mortality. We have not seen the excess relapse rate reported when patients are given a non myeloablative regimen, and disease control has been satisfactorily both for patients in remission, as well as for patients with active disease at the time of transplants.

No relevant conflicts of interest to declare.