A two-step approach to myeloablative haploidentical transplantation: low nonrelapse mortality and high survival confirmed in patients with earlier stage disease.

Haploidentical hematopoietic stem cell transplantation (HSCT) is an attractive alternative donor option based on the rapid availability of an acceptable donor for most patients and decreased cost compared with costs of other alternative donor strategies. The safety of haploidentical HSCT has increased in recent years, making it ethically feasible to offer to patients with earlier stage disease. We developed a 2-step approach to haploidentical HSCT that separates the lymphoid and myeloid portions of the graft, allowing fixed T cell dosing to improve consistency in outcome comparisons.

A 2-step approach to myeloablative haploidentical stem cell transplantation: a phase 1/2 trial performed with optimized T-cell dosing.

Studies of haploidentical hematopoietic stem cell transplantation (HSCT) have identified threshold doses of T cells below which severe GVHD is usually absent. However, little is known regarding optimal T-cell dosing as it relates to engraftment, immune reconstitution, and relapse. To begin to address this question, we developed a 2-step myeloablative approach to haploidentical HSCT in which 27 patients conditioned with total body irradiation (TBI) were given a fixed dose of donor T cells (HSCT step 1), followed by cyclophosphamide (CY) for T-cell tolerization.