Disappearance of Ph1-positive cells in four patients with chronic granulocytic leukemia after chemotherapy, irradiation and marrow transplantation from an identical twin.

Four patients (21, 41, 13 and 38 years of age) with a history of chronic granulocytic leukemia for 12, 10, 11, and 106 months, respectively, were treated with dimethyl busulfan, cyclophosphamide, 920 rads of total-body irradiation and intravenous marrow infusion from normal, genetically identical twins. Serial chromosome analyses were performed on marrow aspirates cultured without mitotic stimulants. No Ph1-positive cells were detected in the marrows from the normal twins, whereas just before therapy, all 100 metaphases examined from each patient were Ph1-positive. Chromosome analyses were performed three to five times per patient after transplantation, and not a single Ph1-positive cell was detected. The patients remain hematologically normal 22, 23, 26 and 31 months after transplantation. The results show that the Ph1-positive clone can be eradicated by vigorous therapy and that the marrow in chronic granulocytic leukemia can be repopulated by stem cells from normal twins.