Chimerism analysis in peripheral blood using indel quantitative real-time PCR is a useful tool to predict post-transplant relapse in acute leukemia

Abstract

Detection of increasing mixed chimerism (IMC) using standard PCR correlates with relapse after allo-SCT for acute leukemias (ALs). Quantitative real-time PCR of insertion/deletion polymorphism (indel qrtPCR) is a much more sensitive method, which can be performed on peripheral blood. We studied the significance of low increases of recipient cells (0.1%) detected by indel qrtPCR in a cohort of 89 transplants. We did not observe relapse among the 32 patients with no IMC. Fifty-seven patients presented a first IMC, which was followed by four different scenarios: a decreasing MC (26 cases, no relapse), a stable MC (1 case, 1 relapse), a second IMC (24 cases, 15 relapse) or no control of chimerism (6 cases, 5 relapses). In multivariate analysis, detection of two successive IMCs was strongly associated with relapse (hazard ratio (HR): 9.4, 95% confidence interval (CI): 3.8-23; Po0.0001). Among the 57 patients who presented at least one IMC, 27 underwent immunomodulation (tapering of immunosuppression or donor lymphocyte injection), leading to a 1-year relapse rate of 15.7% vs 57.6% in the 30 other patients (P = 0.0007). Altogether, these results indicate that chimerism analysis using indel qrtPCR in peripheral blood is a useful tool for detection of relapse in patients transplanted for AL.

Highly sensitive chimerism detection in blood is associated with increased risk of relapse after allogeneic hematopoietic cell transplantation in childhood leukemia

“…Recipient DNA in low levels could be caused by surviving leukemic blasts, host hematopoietic cells, cells of non‐hematopoietic origin, or a combination of these. Most studies of RQ‐PCR chimerism have used absolute detection levels of 0.1%‐1% recipient DNA as clinically relevant cutoffs, although results from definitions based on increasing donor DNA rather than absolute levels have been reported in adults . In our study, we detected stable recipient DNA at least once during follow‐up in all children and 56% (347/610) of samples had values above detection limit.…”

“…This is supported by a recent study showing an increased proportion of T regulatory cells in patients with mixed compared to full donor chimerism . Thus, highly sensitive, sequential measurements of chimerism could provide information on the potency of the graft‐versus‐leukemia effect, with the potential of guiding interventions aimed at strengthening this effect …”

“…In conclusion, we find that RQ‐PCR chimerism may be a useful tool for early prediction of relapse in children transplanted for AML and ALL, and thus an alternative to frequent sampling of bone marrow for MRD analysis. Using a very low cutoff of an increase of 0.05% recipient DNA could possibly identify children at high risk of relapse several months prior to overt relapse, leaving time for intensified follow‐up or therapeutic intervention in order to revert an impending relapse …”

Systematic comparison of donor chimerism in peripheral blood and bone marrow after hematopoietic stem cell transplantation

“…1, 2 Sensitive chimerism quantification may therefore allow for early therapeutic intervention, potentially improving treatment response. 3, 4 Frequently, post-HSCT chimerism monitoring involves bone marrow (BM) biopsies, although hematologic malignancies are frequently associated with risk factors for adverse events (for example, low platelet count) and dry taps can preclude chimerism analyses. 5, 6 However, new PCR strategies for chimerism quantification have dramatically increased technical sensitivity with current methods enabling the detection of chimerism below 0.1%.…”

A semi-nested real-time PCR method to detect low chimerism percentage in small quantity of hematopoietic stem cell transplant DNA samples

“…This fact has important consequences in the clinical application of real-time for chimerism, where usually only 3 replicates are performed. Jacque et al (2015), using a genomic real time approach with 250 ng of input DNA (Alizadeh et al 2002) had demonstrated that an increase of chimerism of 0.1% could be useful to exclude all the cases of the relapse. However, considering the higher cost and time consuming of the proposed protocol, compared to the standard one, we suggest to use the sNAS-qPCR method only when low DNA input amount is available, as in the case of blood cell subset samples.…”