Day + 30 detection of minimal residual FLT3-ITD by high-sensitivity PCR-NGS predicts relapse risk and guides...

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has improved outcomes in patients with acute myeloid leukemia (AML) harboring FLT3-internal tandem duplication (FLT3-ITD) mutations. However, relapse still occurs in 15-35% of these patients after transplantation. Therefore, early and highly sensitive detection methods are required to identify patients at risk of relapse and enable timely post-transplant intervention.

In this NICHE cohort study, a total of 136 patients were included, then we evaluated whether high-sensitivity polymerase chain reaction (PCR)-next-generation sequencing (NGS) for FLT3-ITD (limit of detection: 5 × 10^-6) on day + 30 post-HSCT could identify patients at a high risk of relapse and inform decisions regarding maintenance therapy.

Among the 136 patients, 37 patients (27.2%) had detectable FLT3-ITD clones on day + 30. These patients exhibited a significantly higher cumulative incidence of post-HSCT multiparameter flow cytometry (MFC)-measurable residual disease (MRD) relapse (40.3% vs. 18.8%, p = 0.001). Notably, FLT3-ITD-positive patients who received FLT3 inhibitor maintenance therapy had no relapses, while 6 out of the 13 patients who did not receive maintenance therapy relapsed. Conversely, FLT3-ITD-negative patients without high-risk factors (2022 European LeukemiaNet adverse-risk group, relapsed/refractory AML, MFC-MRD positivity pre-HSCT) showed limited benefit from maintenance therapy (MFC-MRD-free survival: hazard ratio (HR) = 0.25 (0.03-2.11), p = 0.204; OS: HR = 0.20 (0.02-1.70), p = 0.142).

This is the first study to demonstrate that detection of minimal FLT3-ITD clones at the fixed time point of day + 30 post-HSCT can reliably stratify relapse risk in AML patients and provide a rationale for individualized post-transplant maintenance therapy.