Post-Transplant Relapse in Acute Leukemia: Comparative Value of MRD and Chimerism

Relapse remains the principal cause of treatment failure after allogeneic hematopoietic stem cell transplantation (AHSCT) in acute leukemia. Post-transplant surveillance commonly relies on measurable residual disease (MRD) and donor chimerism monitoring; however, their relative predictive value and optimal timing remain uncertain.

To compare the prognostic performance of MRD and donor chimerism in predicting relapse after AHSCT in adult patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL).

This retrospective cohort included 264 adults (186 AML, 78 ALL) who underwent AHSCT. MRD was assessed by multiparametric flow cytometry on day 28 and at months 3 and 12, and chimerism by short tandem repeat PCR. Cox regression identified independent relapse predictors.

Relapse occurred in 95 patients (68 AML, 27 ALL). In AML, MRD positivity at month 3 (HR 3.69, p<0.001) and mixed total chimerism at month 3 (HR 2.47, p=0.029) independently predicted relapse and were associated with inferior overall and disease-free survival. MRD detected relapse earlier and with greater sensitivity than chimerism. In ALL, total mixed chimerism at month 3 was associated with relapse in univariate analysis, whereas MRD showed limited statistical power due to small sample size.

Post-transplant MRD monitoring at month 3 provides superior risk stratification compared with chimerism in AML. In ALL, both approaches appear complementary, but conclusions are limited by cohort size. Disease-specific, risk-adapted surveillance strategies are warranted.