Impact of Day 14 Peripheral Blood Chimerism after Allogeneic Hematopoietic Stem Cell Bone Transplantation on the Treatment Outcome of Non-Malignant Disease

BACKGROUND: The impact of early peripheral blood chimerism on the outcome of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is unclear. We aimed to determine whether day 14 peripheral blood chimerism after allo-HSCT predicts outcomes in patients with non-malignant diseases. METHODS: Data from 56 patients who received allo-HSCT between April 2007 and March 2016 were retrospectively analyzed. Chimerism was evaluated using short-tandem repeat polymerase chain reaction, with mixed chimerism (MC) defined as greater than 1% recipient cells which was further categorized into low-level MC (> 1% and < 15% of recipient-derived cells) and high-level MC (≥ 15% of the recipient-derived cells). RESULTS: Thirty-six patients showed complete donor chimerism (CC), 14 low-level MC, and 6 high-level MC at day 14 post-transplant. The estimated 5-year event-free survival (EFS) was higher in the CC or low-level MC groups than in the high-level MC group (86.1% vs. 71.4% vs. 33.3%; P = 0.001). In BM or peripheral blood stem cell (BM/PBSC) transplants, the 5-year EFS was higher in the CC or low-level MC group than in the high-level MC group (93.1% vs. 66.7% vs. 0%; P < 0.001). However, in cord blood transplants, the 5-year OS and EFS according to the day 14 peripheral blood chimerism did not reach statistical significance. CONCLUSION: Although CC is not always necessary after allo-HSCT for non-malignant diseases, our data suggest that day 14 peripheral blood chimerism may predict outcomes in patients with non-malignant diseases who underwent BM/PBSC transplants.

Clinical implications of chimerism after allogeneic hematopoietic stem cell transplantation in children with non-malignant diseases / 대한혈액학회지

BACKGROUND: The effects of chimerism on outcomes following allogeneic hematopoietic stem cell transplantation (HSCT) are unclear and may differ between diseases. We retrospectively evaluated the association between chimerism and transplant outcomes in children with nonmalignant diseases. METHODS: Chimerism was evaluated using short-tandem repeat polymerase chain reaction (STR-PCR) in 48 patients, with mixed chimerism (MC) defined as greater than 1% recipient cells. RESULTS: The only variable exerting a significant influence on patients' chimerism status was the number of infused CD34+ cells. MC was detected in 23 transplants (9 showing transient MC; 10 with sustained low levels [30%]). The degree of STR-PCR at 28 days after HSCT was significantly higher in patients with high-level MC than those with transient or low-level MC. All patients with transient or low-level MC successfully maintained engraftment and showed a clinical response to HSCT, whereas 2 of the 4 patients with high-level MC experienced graft failure. The incidences of grades II-IV acute and chronic graft-versus-host disease (GVHD) were significantly higher in patients with complete donor chimerism (CC) than MC. We observed no significant survival differences between CC and MC groups. However, the survival rate was lower in patients with high MC than those with low-level or transient MC (P=0.03). CONCLUSION: In non-malignant diseases, MC may indicate a tolerant state with a decreased incidence of GVHD. However, high-level MC may signify an increased risk of graft failure and a lower survival rate.