A comparison of flow cytometry detection of minimal residual disease and chimerism kinetics in chronic lymphocytic leukemia patients after allogeneic hematopoietic stem cell transplantation

Determination of minimal residual disease (MRD) remains crucial for the follow-up after therapy in chronic lymphocytic leukemia (CLL) patients. Chimerism was assessed by short tandem repeat (STR)PCR and single nucleotide polymorphisms (SNP)PCR, and MRD by a multicolor flow cytometric approach in 12 consecutive patients with CLL after they received allogeneic stem cell transplantation (SCT). Overall, 11 patients achieved MRD flow negativity [10 had full donor chimerism (FDC) and one had mixed chimerism (MC)]. Only one patient remained with MRD flow positivity and displayed MC. Fiftysix samples were concomitantly studied by both chimerism and MRD flow. A significant correlation was observed between MRD flow data and chimerism in both PB and BM by using a mixed effect linear regression (p < 0.001). Flow cytometry approach of MRD can be easily combined with chimerism during the follow-up post-allogeneic SCT. Both techniques appeared complementary for guiding post-transplant immunomodulation.