OVERVIEW
Core binding factor AMLs (those with t(8;21), t(16;16), or inv16) and those with a mutated NPM1 (in the absence of unfavourable biomarkers) are classified by NCCN as having a favourable risk profile. This notwithstanding, 5yr overall survival remains at only 65%. MRD monitoring not only provides reassurance to the majority of patients but also provides the opportunity for earlier intervention (or planning) in the event of molecular relapse.
INDICATION
Reflex test (baseline) in new AML patients found to harbour inv16, t(16;16), t(8;21), or select NPM1 variants.
Measurable residual disease (MRD) monitoring following initiation of treatment.
REFERRAL
Any reviewing hematopathologist or treating hematologist
TEST REQUIREMENTS
- Completed CGL Myeloid Testing requisition form [link]
This test is routinely performed at diagnosis and then a monthly intervals post consolidation for two years. It is understood that, at the time of diagnostic sample collection, the presence or absence of these biomarkers is not known. It remains that both an EDTA bone marrow and an EDTA peripheral blood should be forwarded to CGL. These will be extracted to RNA and are not suitable for either FLT3 mutation testing or myeloid panel based mutation screening.
2a. At diagnosis and post consolidation
- 20mL Peripheral Blood in EDTA tubes (purple top); destined for RNA
- 5mL Bone marrow aspirate in EDTA tubes (purple top); destined for RNA
2b. At all other time points
- 20mL Peripheral Blood in EDTA tubes (purple top); destined for RNA
TRANSPORT
Click here for guidelines on transporting specimens.
METHOD
inv16, t(16;16)
The amount of the CBFB::MYH11 fusion transcript (type A) present in this sample is quantified with respect to BCR transcript using RT-ddPCR (Biorad’s QX200 Droplet Digital PCR System) and expressed as a log ratio. The limit of reliable detection (LOD) of this assay is 4 positive droplets over 4 wells. The sample specific LOD is dependent on the concentration of BCR transcript in that sample and is expressed, when applicable, as a log ratio to BCR. The limit of quantification (LOQ) is 10 positive droplets over 4 wells. Analytically positive results below this limit are reported as positive below the sample specific limit of quantification (log ratio to BCR).
t(8;21)
The amount of the RUNX1::RUNX1T1 fusion transcript present in the sample is quantified with respect to BCR transcript using RT-ddPCR (Biorad’s QX200 Droplet Digital PCR System) and expressed as a log ratio. The limit of reliable detection (LOD) of this assay is 4 positive droplets over 4 wells. The sample specific LOD is dependent on the concentration of BCR transcript in that sample and is expressed, when applicable, as a log ratio to BCR. The limit of quantification (LOQ) is 10 positive droplets over 4 wells. Analytically positive results below this limit are reported as positive below the sample specific limit of quantification (log ratio to BCR).
NPM1
The amount of the NPM1 transcript (variant A, B, or D) present in this sample is quantified with respect to BCR transcript using RT-ddPCR (Biorad’s QX200 Droplet Digital PCR System) and expressed as a log ratio. The limit of reliable detection (LOD) of this assay is 4 positive droplets over 4 wells. The sample specific LOD is dependent on the concentration of BCR transcript in that sample and is expressed, when applicable, as a log ratio to BCR. The limit of quantification (LOQ) is 10 positive droplets over 4 wells. Analytically positive results below this limit are reported as positive below the sample specific limit of quantification (log ratio to BCR).
CLINICAL UTILITY
Presently, this testing is primarily intended to be used for the early identification of relapse following chemotherapy or stem cell transplant. Early identification of molecular relapse as opposed to hematologic or clinical relapse will allow for earlier intervention (e.g. stem cell transplant, withdrawal of immunosuppression post stem cell transplant) with the aim of preventing overt relapse
TURN AROUND TIME
Results are reported within fourteen calendar days from receipt of specimen and completed requisition form.
SELECTED REFERENCES
NCCN Guidelines – AML v1.2022