How is complete molecular response monitored in chronic myelogenous leukemia (CML) taking TKIs?

Updated: Oct 23, 2019
  • Author: Rossa Khalaf, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Molecular response is monitored by quantitative polymerase chain reaction (qPCR) studies on peripheral blood. It is usually performed at diagnosis, then every 3 months until BCR-ABL1 transcripts are < 0.1%, then every 3-6 months. Definitions are as follows:

  • Early molecular response:  BCR-ABL1 transcripts ≤10% at 3 and 6 months after TKI initiation
  • Major molecular response:  BCR-ABL1 transcripts < 0.10%
  • Deep molecular response: No detectable  BCR-ABL1 transcripts

According to the National Comprehensive Cancer Network (NCCN), the response milestones that should be achieved are the following [19] :

  • BCR-ABL1 transcripts of 1%-10% at 3 or 6 months
  • BCR-ABL1 transcripts of 0.1% to < 1% at 12 months
  • BCR-ABL1 transcripts < 0.1% after 12 months

QPCR has high sensitivity and correlates strongly with the results obtained from bone marrow studies, so it can obviate bone marrow biopsy during treatment. [29] However, if qPCR is not available, then treatment monitoring should use bone marrow cytogenetics. [27, 28]

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