Donor-Cell Leukemia After Hematopoietic Stem Cell Transplant: a Retrospective Review of a Single Center's Experience

Abstract 1997

Donor-cell leukemia (DCL) is a rare complication of allogeneic hematopoietic stem cell transplant (ASCT) with a reported incidence varying from 0.1% to 5.0% of all post-transplantation relapses. However, the incidence is likely to be highly underestimated due to the difficulty in making the diagnosis. In the 1970s and 1980s, diagnosis of DCL relied on cytogenetic and fluorescence in situ hybridization studies in sex-mismatched donor/recipient pairs. Recent advances in molecular-based laboratory methods have considerably improved our ability to identify and confirm DCL in ASCT patients, especially when there is not a sex-mismatch between donor and recipient. Recently, an algorithm has been proposed by Wang et al. 2011 (Am J Clin Pathol 135;525–40) to help make the diagnosis of DCL in ASCT patients who develop overt leukemia or a clonal cytogenetic abnormality using these new advanced techniques. We retrospectively evaluated all patients who underwent ASCT at our center for acute leukemia from 2005 to present. Out of 43 patients, 6 apparent DCLs were documented using short tandem repeat (STR) analysis (12 separate loci examined); each ASCT patient relapsed with the full complement of donor STRs. Our data confirms that the true incidence of DCL is likely underestimated, since within our select population, we had a 14% incidence of DCL. Of note, 1/6 were sex mismatches, 3/6 received cord blood transplants, 4/6 cases were ABO mismatches, and 4/6 cases were AML (Table 1). Our findings concur with sparse available reports in the literature that purport there may be a shorter time to relapse in patients who are undergoing ASCT for malignant reasons; indeed, our average latency period was 14 months as opposed to 24 months found by Wang et al. However, we did not find that a disproportionate number of sex-mismatched donor/recipient pairs developed DCL; in fact, nearly all of our DCLs arose in the setting of a sex-matched pair. The apparent increased incidence in cord blood transplants, sex-mismatched donor/recipient pairs and ABO-mismatched transplants needs to be assessed in a large-scale registry using standard methodologies, which could help identify and define potential causes of DCL.