Transient mixed chimerism after stem cell transplantation can induce durable molecular complete remissions in chronic...

Three patients with BCR/ABL+ chronic myelogenous leukemia were allografted, two with unrelated compatible placental blood and one from a human leukocyte antigen compatible sibling. The patients engrafted successfully, achieved mixed chimerism and all cleared the BCR/ABL fusion transcript. Despíte the fact that the three patients lost the chimerism, they have remained in complete molecular remissions 9 months, 16 months and 5 years, respectively, after the allografts. It is possible that the transient induction of a graft-vs.-leukemia effect was able to control the malignancy despite the fact that the three patients lost the graft; however, other possible explanations are discussed. A longer follow-up of the patients is mandatory to further clarify these observations.