Reverse Transcription Polymerase Chain Reaction
- Recommended when submitting initial diagnostic specimen for CML or Ph+ ALL when the BCR-ABL1 fusion form is not known (no previous BCR-ABL1 testing performed) or is unclear
- If qualitative test is positive for the presence of the p210 (major breakpoint), p190 (minor breakpoint), or p230 (micro breakpoint), the corresponding quantitative test is performed
Quantitative Reverse Transcription Polymerase Chain Reaction
- Appropriate for diagnosis and monitoring of individuals with CML or a subset of B-cell ALL
- BCR-ABL1 major (p210) fusion form is present in almost all cases of CML and in a subset of ALL cases (e13a2 or e14a2 transcripts)
Quantitative Reverse Transcription Polymerase Chain Reaction
Useful in cases of Philadelphia chromosome positive (Ph+) ALL to quantify the BCR-ABL1 p190 fusion form
Related Tests
Massively Parallel Sequencing
- Useful for patients with an established diagnosis of a BCR-ABL1 positive (Ph+) leukemia to determine if a mutation is present that would interfere with response to TKI therapy in Ph+ ALL or CML
- Detects all common mutations, including T315I
- Provides higher sensitivity than traditional Sanger sequencing techniques
- Offers coverage of SH2, SH3, and kinase domains
Massively Parallel Sequencing
Assess for gene mutations, including substitutions and insertions and deletions that may have diagnostic, prognostic, and/or therapeutic significance
Fluorescence in situ Hybridization (FISH)
Recommended FISH panel for children with newly diagnosed ALL
Fluorescence in situ Hybridization (FISH)
Recommended FISH panel for adults with newly diagnosed ALL
Fluorescence in situ Hybridization (FISH)
- Use to order individual or multiple oncology FISH probes if standard FISH panels are not desired
- The specific probe for t(9;22); BCR-ABL1 must be requested
Polymerase Chain Reaction/Fluorescence Monitoring
Enzymatic/Quantitative Liquid Chromatography-Tandem Mass Spectrometry
Quantitative Liquid Chromatography/Tandem Mass Spectrometry
Immunoturbidimetry
BCR-ABL1 quantitative testing is recommended for patients with either chronic myelogenous leukemia (CML), a hematopoietic stem cell disease, or acute lymphoblastic leukemia (ALL), an aggressive type of leukemia of either B- or T-lineage immature lymphoid cells. In CML, identification of BCR-ABL1 fusion genes is used for diagnosis and ongoing therapeutic monitoring. Massively parallel sequencing is used to identify gene mutations that may interfere with the effectiveness of tyrosine kinase inhibitor (TKI) therapy and to determine management strategy. In ALL, BCR-ABL1 fusion identification is used for risk stratification treatment decisions. Sequencing is used for minimal residual disease (MRD) assessment of Philadelphia chromosome positive (Ph+) ALL.
Typical Testing Strategy
Chronic Myelogenous Leukemia
- Bone marrow cytogenetic studies and quantitative reverse transcription polymerase chain reaction (RT-PCR) measurement of BCR-ABL1 transcript levels recommended before treatment initiation
- Quantitative RT-PCR is used to monitor response to TKI therapy
- BCR-ABL1 kinase domain mutation analysis (massively parallel sequencing) is useful to monitor TKI therapy and disease progression
Acute Lymphoblastic Leukemia
- Evaluation for the presence of recurrent genetic abnormalities at diagnosis using karyotyping and/or fluorescence in situ hybridization (FISH) assays
- MRD assessment on bone marrow using flow cytometry and quantitative RT-PCR at the completion of therapy and at regular intervals to monitor progress
Disease Overview
Chronic Myelogenous Leukemia
Incidence
Acute Lymphoblastic Leukemia
Incidence
- 75-80% of acute leukemias in children
- 20% of adult leukemias
Treatment Issues
The goal of TKI therapy is to achieve a complete cytogenetic response within 12 months of initiation of therapy with goal of eventual major molecular response. A subset of individuals will eventually achieve a complete molecular response (undetectable BCR-ABL1 transcripts using a test with 4.5 log sensitivity).
Prognostic Issues
A 3-log decrease in the level of BCR-ABL1 fusion transcripts (major molecular response) within 18 months of beginning TKI therapy is an indicator of favorable outcome. Monitoring for recurrence using quantitative measures is crucial for detecting early relapse.
Genetics
Gene
BCR-ABL1
Mutations
- >130 mutations
- Four regions tested
- Adenosine triphosphate binding-loop (P-loop)
- Drug-binding sites
- Catalytic domain
- Activation loop
Test Interpretation
BCR-ABL1, Major (p210), Quantitative
Analytical Sensitivity
1:125,000 normal cells (chart)
Results
Result | Variant(s) Detected | Interpretive Data |
---|---|---|
Positive |
BCR-ABL1 fusion transcripts (p210) detected |
BCR-ABL1/ABL1 quantitative ratio is provided (normalized copy number) Results also reported in terms of BCR-ABL1 international scale (IS) |
Weakly positive |
BCR-ABL1 fusion transcripts detected below the limit of quantitation |
BCR-ABL1 to ABL1 ratio cannot be calculated IS result <0.0069% |
Not detected |
No BCR-ABL1 fusion transcripts detected |
Does not exclude BCR-ABL1 fusion transcripts (p210) below the test limit of detection Does not exclude BCR-ABL1 fusion transcripts not detected by this test (p190 or p230) |
Limitation
Does not detect p190.
BCR-ABL1, Minor (p190), Quantitative
Analytical Sensitivity
1:125,000 normal cells (chart)s
Results
Result | Variant(s) Detected | Interpretive Data |
---|---|---|
Positive |
BCR-ABL1 fusion transcripts (p210) detected |
BCR-ABL1/ABL1 quantitative ratio is provided (normalized copy number) |
Weakly positive |
BCR-ABL1 fusion transcripts detected below the limit of quantitation |
BCR-ABL1 to ABL1 ratio cannot be calculated |
Not detected |
No BCR-ABL1 fusion transcripts detected |
Does not exclude BCR-ABL1 fusion transcripts (p190) below the test limit of detection Does not exclude BCR-ABL1 fusion transcripts that are not detected by this test (p210 or p230) |
References
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NIH - Chronic myeloid leukemia
National Institutes of Health, U.S. National Library of Medicine. Genetics Home Reference: chronic myeloid leukemia. [Reviewed: Sep 2016; Accessed: Jul 2020]
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NCCN - Chronic myeloid leukemia v3.2020
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Chronic myeloid leukemia. Version 3.2020. [Updated: Jan 2020; Accessed: Jul 2020]
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NCCN - Acute lymphoblastic leukemia v1.2020
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Acute lymphoblastic leukemia. Version 1.2020. [Updated Jan 2020; Accessed: Jul 2020]