Does Day 14 Peripheral Blood Chimerism after Allogeneic Hematopoietic Stem Cell Transplantation Predict Treatment Failure in Children with Non-Malignant Disease?

Abstract

The impact of early time peripheral blood chimerism on the outcome of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is unclear. This study was aimed to identify if day 14 peripheral blood chimerism is associated with transplant outcomes in children with non-malignant disease. Data from 52 patients who received allo-HSCT between October 2006 and April 2015 at Samsung Medical Center were retrospectively analyzed. Chimerism was evaluated using short-tandem repeat polymerase chain reaction, with mixed chimerism defined as greater than 1% of recipient cells. Event was defined as death, primary engraftment failure, late rejection, and progression of primary disease. A total of 52 patients underwent 56 transplantations and their median follow-up duration was 28 months (range, 1-91). Of 56 transplants, 24 (42.9%) showed mixed chimerism (MC) and 32 (57.1%) showed complete donor chimerism (CC) at day 14 post-transplant. The estimated event-free survival (EFS) at 2-year was higher in day 14 CC group as compared with MC group (80.5% vs. 53.3%, P = 0.047) while their 2-year overall survivals were similar (80.5% vs. 72.8%, P = 0.711). Among 34 transplants achieving bone marrow CC at 1 mo post-transplant (28 CC and 6 MC at day 14), those with day 14 peripheral blood CC showed better EFS than those with MC (81.4% vs. 20.8%, P= 0.026). Although CC is not always necessary after allo-HSCT for non-malignant disease, our data suggest that early peripheral blood chimerism may serve as a predictor of transplant outcomes in children with non-malignant disease.