🧬 2025 ELN–DAVID MRD Update in AML Major practical changes every hematologist should know 👇🧵 1️⃣ MRD is no longer simply positive or negative 🔵 MRD-negative → optimal response 🟡 MRD low-level positive (MRD-LL) → warning 🔴 MRD-positive → high risk of treatment failure Interpretation depends on the assay, marker, specimen and time point—not one universal cutoff. 2️⃣ Choose the assay according to AML biology 🧬 NPM1 → qPCR 🧬 RUNX1::RUNX1T1 / CBFB::MYH11 → qPCR 🧬 PML::RARA → qPCR 🧬 FLT3-ITD → ultrahigh-sensitivity NGS 🔬 Other AML → multiparameter flow cytometry (MFC) 🧪 Other mutations → validated UHS-NGS when available 3️⃣ Core MRD time points 📍 Diagnosis: establish baseline marker/LAIP 📍 After 2 intensive chemotherapy cycles 📍 Before allo-HCT 📍 End of treatment (EOT) 📍 Serial follow-up MRD must be interpreted using the recommended tissue at each time point. 4️⃣ Sample quality matters 🦴 Use the first bone-marrow aspirate pull—or the first pull after repositioning the needle. 🧪 Maximum preferred volume: 5 mL ⚠️ Hemodilution can produce falsely reassuring MRD results. 📋 Record sample quality, cellularity, assay sensitivity, LOD and LOQ. 5️⃣ MFC-MRD thresholds 🟢 <0.01% or below LOD → MRD-negative 🟡 0.01% to <0.1% → MRD-LL / warning 🔴 ≥0.1% → MRD-positive / high risk of treatment failure ✅ Reliable negativity requires assessment of ≥500,000 CD45⁺ cells using the best available LAIP/DfN abnormality. 6️⃣ Mutated NPM1 after 2 cycles or before allo-HCT—use PB 🟢 <0.001% → optimal 🟡 0.001% to <0.01% → MRD-LL / warning 🟠 ≥0.01% → MRD-positive, but still classified as warning at this early time point ⚠️ Do not automatically label early PB positivity as treatment failure. 7️⃣ Mutated NPM1 at EOT—use BM 🟢 <0.001% → optimal 🟡 0.001% to <0.1% → warning 🔴 ≥0.1% → high risk of treatment failure 📉 The previous 2% threshold has been lowered markedly to permit earlier recognition of high-risk disease. 8️⃣ Core-binding-factor AML 🧬 Establish the diagnostic BM transcript level. After 2 cycles/before allo-HCT: ✅ ≥3-log reduction → optimal ⚠️ <3-log reduction → warning At EOT: 🟢 Undetectable/<0.001% → optimal 🟡 Detectable with ≥3-log reduction → warning 🔴 <3-log reduction → high risk of treatment failure 9️⃣ FLT3-ITD has become an important MRD marker 🔬 Use UHS-NGS with sensitivity approximately 10⁻⁴–10⁻⁵. 📍 Strongest evidence: after 2 cycles and before allo-HCT 🦴 BM is preferred over PB 🔴 Detection ≥ assay LOD → high risk of treatment failure Evidence at EOT and during follow-up remains more limited but supports monitoring. 🔟 Do not misclassify clonal hematopoiesis as AML MRD 🚫 Persistent DNMT3A, TET2 or ASXL1 mutations should generally not define MRD after chemotherapy or before allo-HCT. 🧬 Germline-predisposition variants also require cautious interpretation. ✅ Use leukemia-specific, technically validated markers whenever possible. 1️⃣1️⃣ MRD-directed clinical action 🟢 Optimal response → continue treatment according to baseline ELN risk. In ELN-intermediate AML, the value of allo-HCT may be discussed individually. 🟡 Warning/MRD-LL → continue planned therapy—including allo-HCT when indicated—and monitor closely. 🔴 High-risk response or MRD relapse → strongly consider urgent therapeutic intervention or a clinical trial. 1️⃣2️⃣ Transplant messages ✅ Pre-HCT MRD positivity is not a contraindication to allo-HCT. 🔥 Consider myeloablative conditioning when clinically suitable. 💊 FLT3-ITD MRD positivity before/after allo-HCT supports post-transplant FLT3-inhibitor maintenance. 🔬 MFC monitoring: during the first post-HCT year. 🧬 qPCR/UHS-NGS monitoring: generally for 24 months. 📆 Suggested surveillance when applicable: 🩸 PB every 4–6 weeks for 24 months 🦴 BM every 3 months for ≥24 months 🔬 MFC-based BM monitoring commonly every 3 months for 12 months