Measurable residual disease (MRD) monitoring is used to guide therapy in CML, AML and ALL. Fusion-driven subtypes with available MRD testing include PML-RARA, RUNX1-RUNX1T1, CBFB-MYH11 and BCR-ABL1. MRD testing for the three main NPM1 variant subtypes (A, B and D) is also available.
Assessment of a pre-treatment diagnostic sample is important to identify the precise fusion transcript type and as a future reference point.
A repeat sample should always be tested if a significant change in transcript levels is observed to confirm this change prior to any alteration in therapeutic decision making.
There have been rare reports of cytogenetics/FISH-negative PCR-positive gene fusions, therefore confirmatory testing by PCR may also be helpful if initial testing is unexpectedly negative or uninformative.