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European LeukemiaNet laboratory recommendations for the diagnosis and management of chronic myeloid leukemia

ELN · 2023 · Europe

Source and licence

Authors
Nicholas C. P. Cross, Thomas Ernst, Susan Branford et al.
Title
European LeukemiaNet laboratory recommendations for the diagnosis and management of chronic myeloid leukemia
Journal
Leukemia, 2023
DOI
10.1038/s41375-023-02048-y
Licence
CC BY 4.0
Changes
Verbatim excerpts; formatting adapted

Full text retrieved 2026-10-27 from Europe PMC · PMC10624636

Licence statement of the original publication

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This page reproduces excerpts of the original publication; the original is authoritative. It has not been reviewed by a physician, does not state a recommendation of Medelix and does not replace medical advice. The guideline may have been updated since.

Open the original publication →Full text on Europe PMC

Recommendations

Verbatim, with grade of recommendation or strength of consensus where given.

Diagnostic work up and pre-treatment tests

  • RecommendationsCytogenetics along with FISH and/or RT-PCR should be used in all cases to confirm a diagnosis of CML. The limitations of each approach as standalone tests need to be understood and, where appropriate, included in clinical reports. Cytogenetic testing should include a screen for ACAs at diagnosis. BCR::ABL1 mRNA transcript type should be determined for all cases prior to treatment to enable appropriate follow up. The possibility of a rare BCR::ABL1 variant should be excluded. If testing for rare variants is not available, the diagnostic report should clearly state that the presence of a BCR::ABL1 remains a possibility and that further testing in an appropriate reference laboratory should be performed.

Recommendations:

  • Cytogenetics along with FISH and/or RT-PCR should be used in all cases to confirm a diagnosis of CML. The limitations of each approach as standalone tests need to be understood and, where appropriate, included in clinical reports.
  • Cytogenetic testing should include a screen for ACAs at diagnosis.
  • BCR::ABL1 mRNA transcript type should be determined for all cases prior to treatment to enable appropriate follow up.
  • The possibility of a rare BCR::ABL1 variant should be excluded. If testing for rare variants is not available, the diagnostic report should clearly state that the presence of a BCR::ABL1 remains a possibility and that further testing in an appropriate reference laboratory should be performed.

Diagnostic work up and pre-treatment tests

  • RecommendationsGene panel analysis pretreatment, including ASXL1 mutation screening, is not currently recommended for routine clinical management but should be performed in investigational studies. NGS panel analysis for patients who present in, or progress to, BP is recommended to identify potential targets for treatment in addition to BCR::ABL1.

Recommendations:

  • Gene panel analysis pretreatment, including ASXL1 mutation screening, is not currently recommended for routine clinical management but should be performed in investigational studies.
  • NGS panel analysis for patients who present in, or progress to, BP is recommended to identify potential targets for treatment in addition to BCR::ABL1.

Molecular monitoring of measurable residual disease

  • RecommendationsMRD analysis for CML should use ABL1, BCR or GUSB as internal reference genes. RT-dPCR is an acceptable alternative to RT-qPCR and may offer some technical advantages, particularly for assessment of very low-level disease. MRD results using RT-qPCR or RT-dPCR should be expressed on the International Scale for BCR::ABL1 measurement for e13a2/e14a2 BCR::ABL1 patients. For assessment of deep molecular response, tests should be optimised to achieve a limit of detection of MR4.5 or better using clinical samples, without compromising the limit of blank (background false positive rate). Ongoing internal quality control is essential to monitor assay stability over time. Patients expressing atypical BCR::ABL1 fusions should be monitored by bespoke RT-qPCR or RT-dPCR assays and results expressed as individual molecular responses compared to baseline levels. FISH is not recommended as this technique has very limited sensitivity compared to molecular monitoring but it may be useful if molecular tests for atypical fusions are not available.

Recommendations:

  • MRD analysis for CML should use ABL1, BCR or GUSB as internal reference genes. RT-dPCR is an acceptable alternative to RT-qPCR and may offer some technical advantages, particularly for assessment of very low-level disease.
  • MRD results using RT-qPCR or RT-dPCR should be expressed on the International Scale for BCR::ABL1 measurement for e13a2/e14a2 BCR::ABL1 patients.
  • For assessment of deep molecular response, tests should be optimised to achieve a limit of detection of MR4.5 or better using clinical samples, without compromising the limit of blank (background false positive rate).
  • Ongoing internal quality control is essential to monitor assay stability over time.
  • Patients expressing atypical BCR::ABL1 fusions should be monitored by bespoke RT-qPCR or RT-dPCR assays and results expressed as individual molecular responses compared to baseline levels.
  • FISH is not recommended as this technique has very limited sensitivity compared to molecular monitoring but it may be useful if molecular tests for atypical fusions are not available.

BCR::ABL1 mutations and mechanisms of resistance to TKIs

  • RecommendationsTargeted NGS, whenever available or accessible, is the recommended method for BCR::ABL1 TKD mutation testing, provided that a reliable and validated assay has been implemented. Mutation screening should only be performed for cases with BCR::ABL1 mRNA levels ≥0.1% IS, i.e., ELN-defined failure or warning. The recommended input material is RNA from peripheral blood or bone marrow leukocytes. Analysis of genomic DNA is not recommended for routine analysis. Digital PCR may be considered as a first-level screening test for detection of specific mutations of interest when (rapid) TKI switch is needed. The use of Sanger sequencing is acceptable whenever NGS is not available or accessible, and does not represent an inappropriate management of patients. The minimal recommended region to be covered in a broad, untargeted mutation screen for 1st, 2nd and 3rd generation TKIs should focus on the sequence encoding the TKD (residues 232 to 516; Fig. 5). However, for patients resistant to asciminib, mutation screening should be extended to include relevant regions outside the TKD (Table 4).

Recommendations:

  • Targeted NGS, whenever available or accessible, is the recommended method for BCR::ABL1 TKD mutation testing, provided that a reliable and validated assay has been implemented.
  • Mutation screening should only be performed for cases with BCR::ABL1 mRNA levels ≥0.1% IS, i.e., ELN-defined failure or warning.
  • The recommended input material is RNA from peripheral blood or bone marrow leukocytes. Analysis of genomic DNA is not recommended for routine analysis.
  • Digital PCR may be considered as a first-level screening test for detection of specific mutations of interest when (rapid) TKI switch is needed.
  • The use of Sanger sequencing is acceptable whenever NGS is not available or accessible, and does not represent an inappropriate management of patients.
  • The minimal recommended region to be covered in a broad, untargeted mutation screen for 1st, 2nd and 3rd generation TKIs should focus on the sequence encoding the TKD (residues 232 to 516; Fig. 5). However, for patients resistant to asciminib, mutation screening should be extended to include relevant regions outside the TKD (Table 4).

BCR::ABL1 mutations and mechanisms of resistance to TKIs

  • RecommendationsBCR::ABL1 TKD mutation testing is indicated: - In case of failure and warning to 1st or 2nd line TKI therapy according to current ELN clinical recommendations. - In case of relapse (BCR::ABL1IS ≥ 0.1%) after allogeneic stem cell transplant if mutation was detectable prior to transplant. BCR::ABL1 TKD mutation testing is not indicated: - at diagnosis, i.e., before start of any TKI treatment. - at failure after TFR (except for patients not achieving MMR within 3–6 months after restarting TKI therapy when TKD mutation testing is indicated). - In patients with BCR::ABL1IS < 0.1%. In patients on third-line TKI therapy and beyond, BCR::ABL1 TKD mutation testing should be considered when there is no improvement of response after 3–6 months of treatment, and is indicated if response worsens (e.g. ≥5-fold increase of BCR::ABL1ISwith loss of MR3). Sequential monitoring of a positive BCR::ABL1 TKD mutation testing result might be useful in case of low level mutations of unknown or doubtful clinical significance. Resampling should be performed after 1–3 months (depending on response level and kinetics). Sequential monitoring of a positive BCR::ABL1 TKD mutation testing result might also be useful if there is no improvement in response based on standard BCR::ABL1 transcript level monitoring after TKI switch.

Recommendations:

  • BCR::ABL1 TKD mutation testing is indicated: - In case of failure and warning to 1st or 2nd line TKI therapy according to current ELN clinical recommendations. - In case of relapse (BCR::ABL1IS ≥ 0.1%) after allogeneic stem cell transplant if mutation was detectable prior to transplant.
  • - In case of failure and warning to 1st or 2nd line TKI therapy according to current ELN clinical recommendations.
  • - In case of relapse (BCR::ABL1IS ≥ 0.1%) after allogeneic stem cell transplant if mutation was detectable prior to transplant.
  • BCR::ABL1 TKD mutation testing is not indicated: - at diagnosis, i.e., before start of any TKI treatment. - at failure after TFR (except for patients not achieving MMR within 3–6 months after restarting TKI therapy when TKD mutation testing is indicated). - In patients with BCR::ABL1IS < 0.1%.
  • - In patients with BCR::ABL1IS < 0.1%.
  • In patients on third-line TKI therapy and beyond, BCR::ABL1 TKD mutation testing should be considered when there is no improvement of response after 3–6 months of treatment, and is indicated if response worsense.g. ≥5-fold increase of BCR::ABL1ISwith loss of MR3
  • Sequential monitoring of a positive BCR::ABL1 TKD mutation testing result might be useful in case of low level mutations of unknown or doubtful clinical significance. Resampling should be performed after 1–3 monthsdepending on response level and kinetics
  • Sequential monitoring of a positive BCR::ABL1 TKD mutation testing result might also be useful if there is no improvement in response based on standard BCR::ABL1 transcript level monitoring after TKI switch.

BCR::ABL1 mutations and mechanisms of resistance to TKIs

  • RecommendationsMutations detected by Sanger sequencing or detected in ≥15% of transcripts by NGS or dPCR, should trigger consideration of an immediate change of therapy if they are recognized to be resistant to the ongoing TKI. Mutations detected in <15% of transcripts by NGS or digital PCR should trigger consideration of a change of therapy if they are recognized to confer resistance to the ongoing TKI and an immediate TKI change is deemed preferable over a wait-and-watch approach, for example in the context of continually increasing BCR::ABL1IS levels or suspected/overt disease progression. Mutations detected in <15% of transcripts that are not recognized as being recurrent in CML should be confirmed on an independent sample before being considered further. Mutations of unknown clinical relevance (i.e. never reported in the literature) should not trigger an immediate change of therapy unless the clinician deems the risks of continuing the ongoing TKI treatment to be much greater than the benefits (for example, in case of warning). The ‘35ins’ variant should not be reported as a TKI-resistant mutation.

Recommendations:

  • Mutations detected by Sanger sequencing or detected in ≥15% of transcripts by NGS or dPCR, should trigger consideration of an immediate change of therapy if they are recognized to be resistant to the ongoing TKI.
  • Mutations detected in <15% of transcripts by NGS or digital PCR should trigger consideration of a change of therapy if they are recognized to confer resistance to the ongoing TKI and an immediate TKI change is deemed preferable over a wait-and-watch approach, for example in the context of continually increasing BCR::ABL1IS levels or suspected/overt disease progression.
  • Mutations detected in <15% of transcripts that are not recognized as being recurrent in CML should be confirmed on an independent sample before being considered further. Mutations of unknown clinical relevance (i.e. never reported in the literature) should not trigger an immediate change of therapy unless the clinician deems the risks of continuing the ongoing TKI treatment to be much greater than the benefits (for example, in case of warning).
  • The ‘35ins’ variant should not be reported as a TKI-resistant mutation.

Abstract

From the laboratory perspective, effective management of patients with chronic myeloid leukemia (CML) requires accurate diagnosis, assessment of prognostic markers, sequential assessment of levels of residual disease and investigation of possible reasons for resistance, relapse or progression. Our scientific and clinical knowledge underpinning these requirements continues to evolve, as do laboratory methods and technologies. The European LeukemiaNet convened an expert panel to critically consider the current status of genetic laboratory approaches to help diagnose and manage CML patients. Our recommendations focus on current best practice and highlight the strengths and pitfalls of commonly used laboratory tests.

Contents of the original publication

The section headings of the original.

  • Background
  • General laboratory recommendations:
  • Diagnostic work up and pre-treatment tests
  • Cytogenetics
  • Fluorescence in situ hybridization (FISH)
  • Qualitative RT-PCR and BCR::ABL1 isoforms
  • Initial identification of CML patients
  • Features of patients with atypical BCR::ABL1 fusions
  • Recommendations:
  • Genomics and additional genetic abnormalities
  • Genomic abnormalities in BP
  • Technical aspects of NGS
  • Future perspective
  • Recommendations:
  • Molecular monitoring of measurable residual disease
  • The International Scale for BCR::ABL1 measurement
  • Technical considerations
  • Velocity of disease reduction on treatment
  • MRD for patients with atypical BCR::ABL1 transcripts
  • Clinical associations with common BCR::ABL1 isoforms
  • Other approaches to MRD testing
  • Recommendations:
  • BCR::ABL1 mutations and mechanisms of resistance to TKIs
  • Background
  • How to perform BCR::ABL1 TKD mutation testing
  • Recommendations:
  • When to perform BCR::ABL1 TKD mutation testing
  • Recommendations:
  • How to use BCR::ABL1 TKD mutation results
  • Recommendations:
  • BCR::ABL1-independent mechanisms of relapse

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