Usefulness of Post-Transplant Hematopoietic Chimera Monitoring by Use of the Quantitative Fluorescence Polymerase Chain Reaction Method

Influence of Mixed Chimerism on Outcome in Children With Anaemia After Haematopoietic Stem Cell Transplantation

BACKGROUND/AIM

In patients with non-malignant diseases, mixed chimerism is not a rare phenomenon. The clinical impacts of chimerism following allogeneic haematopoietic stem cell transplantation (allo-HSCT) in children with congenital anaemia (CA) and severe aplastic anaemia (SAA) were analysed.

PATIENTS AND METHODS

We studied twenty-seven consecutive children with congenital and acquired anaemia who had undergone allogeneic haematopoietic stem cell transplantations. In the observed group of patients, the median of the follow-up was 6.12 years (2.00-14.8 years).

RESULTS

Overall survival (OS) did not depend on the type of disease p=0.1. OS did not significantly differ in patients who received more than 5x10⁶/kg stem cells (91%) and those who received less than 5x10⁶/kg (85%) (p=0.61). Two patterns of stable mixed chimerism (SMC) were observed: SMC (95-97% cells of the donor), and SMC with a fluctuation between 50-90% of the cells of the donor. None of the surviving patients received immunosuppression treatments of chronic Graft-versus-Host Disease (cGvHD).

CONCLUSION

Our results showed that mixed chimerism did not influence the survival of children with congenital and aplastic anaemia following allo-HSCT.

Impact of early chimerism status on clinical outcome in children with acute lymphoblastic leukaemia after haematopoietic stem cell transplantation

Background

The significance of very early chimerism assessment before day + 28, which is considered the moment of engraftment, is still unclear. In this retrospective study, we evaluated the clinical impact of very early chimerism on the clinical outcome after allogeneic haematopoietic stem cell transplantation (allo-HSCT) in children with acute lymphoblastic leukaemia (ALL).

Methods

The study group included 38 boys and 18 girls. Very early chimerism was evaluated on days + 7, + 14, + 21 and + 28 after the transplant. Short tandem repeat polymerase chain reaction (STR PCR) was used to analyse chimerism.

Results

Overall survival (OS) and event-free survival (EFS) were 84 and 80%, respectively. The OS in the group of 24 patients with complete donor chimerism on day + 14 was 83%, and it did not differ statistically compared to the 32 patients with mixed chimerism on day + 14 (OS was 84%). In our cohort of patients, the matched unrelated donor, male gender of donor, number of transplanted cells above 4.47 × 10⁶ kg and no serotherapy with anti-thymocyte globulin (ATG) were statistically related to a higher level of donor chimerism. The immunophenotypes of disease, age of patient at time HSCT, recipient sex, stem cell source (peripheral blood/bone marrow) and conditioning regimen had no impact on early chimerism. Acute graft versus host disease grades II-IV was diagnosed in 23 patients who presented with donor chimerism levels above 60% on day 7.

Conclusions

The data presented in this study provide valuable insight into the analysis of very early chimerism in children with ALL treated with HSCT.