A prospective study of posttransplant cyclophosphamide for unrelated donor peripheral blood stem cell transplant with special attention to graft content and the impact of a higher γδ T cell dose.

Posttransplant cyclophosphamide (PtCy) has been shown to decrease post-hematopoietic stem cell transplant acute and chronic graft-versus-host disease (GVHD). In this study, PtCy was used in 44 patients along with mycophenolate and tacrolimus with HLA matched (29) and mismatched (15) unrelated donors to determine the impact of graft content on outcome; thus, all patients had flow cytometric analysis of their graft content including the number of B cells, NK cells, and various T cell subsets. Higher γδ T cell dose was associated with the development of acute GVHD (p = .0038). For PtCy, further studies of the cell product along with further graft manipulation, such as selective γδ T cell depletion, could potentially improve outcomes.

A Tender Reduced-Intensity Conditioning for the Unfit: A Novel 4 Gy Total Body Irradiation-Based Conditioning Followed by Two-Step Haploidentical Stem Cell Transplant, Results of a Prospective Trial.

Allogeneic hematopoietic stem cell transplant (HSCT) remains the only potentially curative treatment for many hematologic malignancies (HM). We previously developed a two-step approach that separates the lymphoid and myeloid portions of the graft, allowing a consistent T cell dosing and sparing the stem cells from the effect of post-transplant cyclophosphamide (CY). The two-step approach demonstrated safety and efficacy in patients treated with myeloablative and reduced-intensity conditioning. Here, we extended our two-step platform to older and less fit patients and explored the effects of using a high dose of T cells on disease relapse and transplant outcomes. Thirty-four patients with HM were treated. Median age was 68 years old and included a minority population constituting 32%. Eighty-two percent had a hematopoietic cell transplantation comorbidity index score ≥3. Ninety-one percent were haploidentical, and the rest were matched-related donor HSCT. Following administration of fludarabine and 2 Gy total body irradiation (TBI) (13 patients) or 4 Gy TBI (21 patients) conditioning regimen, a fixed dose of 2 × 108/kg CD3+ T cells was given, followed 2 days later by CY, then infusion of CD34-selected stem cells. Overall survival (OS) was 70% at 1 year and 48% at 3 years. The cumulative incidence (CI) of non-relapse mortality (NRM) and relapse were 22% and 33% at 3 years. However, the CI of relapse was much lower for patients treated with 4 Gy TBI versus those treated with 2 Gy TBI (11% versus 54%, P = .045), while NRM was similar (23% versus 15%, P = .399). This contributed to a high OS of 64% in patients who received 4 Gy TBI-based conditioning at 3 years, with median OS not reached, although this was not statistically significant (P = .68). The median time to neutrophil and platelet recovery was 12 and 17 days, respectively. The CI of grade II acute graft-versus-host-disease (aGVHD) was 22% and 26% at 100 days and 6 months, respectively. The CI of chronic GVHD (cGVHD) was 7.5% at 3 years. There was no grade III or IV aGVHD, no severe cGVHD, and no deaths attributable to GVHD. In conclusion, the two-step approach HSCT demonstrated a low disease relapse rate and high survival in patients treated with 4 Gy TBI-based conditioning, despite a generally older and more medically compromised patient population.