Objective: To explore the relationship between minimal residual disease (MRD) and the outcome of patients with high-risk acute leukemia (AL) undergoing allogeneic hematopoietic stem cell transplantation (HSCT).
Methods: By 4/5-color multi-parameter flow cytometry (MFC, CD45/SSC gating) for detecting MRD at pre-(day-30) and post-transplant (day +30, +60, +100, 6 months, 9 months and 12 months), the investigators retrospectively analyzed the MRD levels and the prognosis of 90 high-risk patients. According to the MRD cutoff value of 0.1%, the low-level and high-level groups were defined. In the high-level group, the patients were divided into two sub groups according to the subsequent treatment (intervention therapy group and non-intervention therapy group).
Results: MRD pre-transplant had no predictive value for the clinical outcome. The patients with high levels of MRD post-transplant (+60 d and +100 d) showed higher relapse rates than those of the low-level group. In addition, regarding MRD +100 d post-transplant, differences were significant among 3 groups (high-level MRD and intervention therapy group, high-level MRD and non-intervention therapy group and low-level MRD group) including 1-year relapse-free survival (RFS) (100% vs 60.87% vs 91.30%, P < 0.05) and 3-year RFS (85.71% vs 44.72% vs 68.48%, P < 0.05). The median time from first high level MRD detected to clinical relapse was 2.5 (1 - 26) months. In the high level MRD group (+100 d post-transplant), 7 of 30 patients received intervention therapy without relapse. However another 23 patients had no intervention treatment and 11 of them relapsed latter (P < 0.05).
Conclusion: The MFC-based quantification of MRD post-transplant reveals important prognostic information in patients with high-risk AL. MRD check point at day +100 (cutoff: 0.1%) may discriminate different risk populations. Those patients with MRD levels ≥ 0.1% should receive early intervention at an early stage and a low tumor burden so as to reduce the relapse rate and boost survival.