Minimal Residual Disease:
Definition: Submicroscopic disease, that remains undetected within the patient even after chemotherapy or bone marrow transplantation, and later can lead to relapse of disease.
Disease is minimal - no signs and symptoms are the disease are present in the patient.
Two types:
Molecular MRD: Detected by PCR only.
Immunophenotypic MRD: Detected by flow cytometry
Applications:
Definition: Submicroscopic disease, that remains undetected within the patient even after chemotherapy or bone marrow transplantation, and later can lead to relapse of disease.
Disease is minimal - no signs and symptoms are the disease are present in the patient.
Two types:
Molecular MRD: Detected by PCR only.
- Real time quantitative PCR is used (RT-PCR)
- Very sensitive.
- Can detect 1 leukemic cell in 1000 - 1000 lakh normal cells
- Detection of fusion transcripts (PML-RARA) or mutations (NPM) or gene overexpressions etc
Immunophenotypic MRD: Detected by flow cytometry
- Uses multiparameter flow cytometry
- Principle: Leukemic cells express an antigen profile different from those observed on normal hematopoietic precursor cells
- MRD expression of markers is compared to the markers expressed in the original disease at diagnosis
- Relies on Leukemia Associated immunophenotypes (LAIP) for diagnosis
- Advantages: Rapid process, widely applicable
Applications:
- Used in AML, ALL, CML, B cell NHL and myeloma
- MRD monitoring is mainly used after induction chemotherapy, post-consolidation, pre-transplant and during CR
- Predicting early relapse, prognostic significance and for therapy decisions
- Risk adjusted therapy:
- 1. To sparse those patients with no residual disease from additional chemotherapy
- 2. To intensify the treatment or consider other options of treatment for those with MRD to avoid relapse.
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