Haploidentical stem cell transplantation in leukemia.

In acute leukemia patients, infusing a megadose of extensively T-cell-depleted hematopoietic stem cells after an immuno-myeloablative conditioning regimen ensures sustained engraftment of full-haplotype mismatched transplants without graft-vs-host disease. Besides the conditioning regimen and the megadose of stem cells donor natural killer cell alloreactivity also plays a role in facilitating engraftment and in preventing relapse. Since our first successful pilot study, our efforts have concentrated on developing new conditioning regimens, optimizing the graft processing and improving the post-transplant immunological recovery. The results we have so far achieved in 112 very high-risk acute leukemia patients show that haploidentical transplantation is now a clinical reality. Because virtually all patients in need of a hematopoietic stem cell transplant have a full-haplotype mismatched donor, who is immediately available, a T-cell depleted mismatched transplant should be offered, not as a last resort, but as a viable option to high risk acute leukemia patients who do not have, or cannot find, a matched donor.