1. ¹National Cancer Institute, Center for Cancer Research, National Institutes of Health, Bethesda, MD, USA
2. ²Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, USA
3. ³Center for International Blood and Marrow Transplant Research, Medical College of Wisconsin, Milwaukee, WI, USA
4. ⁴Division of Cell and Gene Therapies, United States Food and Drug Administration, CBER, Bethesda, MD, USA
5. ⁵Department of Medicine, University of Washington, Seattle, WA, USA
6. ⁶Division of Oncology, Department of Medicine, Washington University School of Medicine, St Louis, MO, USA
7. ⁷Clinic of Hematology, Erasme University Hospital (ULB), Brussels, Belgium
8. ⁸Department of Haematology, Royal Free Hospital and School of Medicine, University College, London, UK
9. ⁹Division of Hematology and Oncology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
10. ¹⁰Division of Adult Stem Cell Transplantation, Texas Transplant Institute, San Antonio, TX, USA
11. ¹¹Department of Hematology-Oncology, Institute of Hematology, Sant' Orsola University Hospital, Bologna, Italy
12. ¹²Department of Hematology, Cliniques Universitaires Saint-Luc, Universite catholique de Louvain, Brussels, Belgium
13. ¹³Department of Hematology, Rigshospitalet University Hospital, Copenhagen, Denmark
14. ¹⁴Department of Stem Cell Transplantation, MD Anderson Cancer Center, University of Texas, Houston, TX, USA
15. ¹⁵National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
16. ¹⁶Department of Hematology, Institute of Hematology and Oncology, Hospital Clinic, IDIBAPS, University of Barcelona, Spain
17. ¹⁷Division of Neoplastic Diseases, Medical College of Wisconsin, Milwaukee, WI, USA

Correspondence: Dr SZ Pavletic, Experimental Transplantation and Immunology Branch, Graft-versus-Host and Autoimmunity Unit, National Cancer Institute, 9000 Rockville Pike, 10 Center Drive, Bethesda, MD 20892-1203, USA. E-mail: pavletis@mail.nih.gov

Received 25 May 2007; Revised 14 July 2007; Accepted 24 July 2007; Published online 30 August 2007.

Abstract

We identified 19 persons with B-cell chronic lymphocytic leukemia (CLL) who received genetically identical twin blood cell or bone marrow transplants after high-dose conditioning. Ten are alive (eight disease-free) with a median follow-up of 89 months (range, 31–171 months); 5-year relapse rate was 50% (95% confidence interval (CI), 26–73%). Estimated 5-year survival and disease-free survival were 61% (95% CI, 37–82%) and 45% (95% CI, 23–68%). In two of four patients tested at 12 and 21 months by polymerase chain reaction no evidence of residual CLL was detected post-transplant. In one recipient who relapsed at 6 years, molecular studies showed a different CLL clone from that detected pretransplant. This clone was subsequently identified in the donor suggesting transfer of occult leukemia at the time of transplant. Genetically identical twin transplants can result in long-term disease-free survival and molecular remissions, these data suggest the potential for CLL control in the absence of allogeneic graft-versus-leukemia effect. The case of leukemia transfer indicates the need for careful evaluation of donors prior to graft collection.