QRT-PCR Molecular Monitoring

QRT-PCR (quantitative real-time polymerase chain reaction) is the most sensitive means of measuring response in CML, able to detect 1 CML cell among≥100,000 normal cells.¹ In patients who have achieved a complete cytogenetic response (CCyR), QRT-PCR is a way to measure the depth of response, as treatment with a tyrosine kinase inhibitor (TKI) often reduces the number of leukemic cells below the threshold that can be detected by cytogenetic analysis.¹

CML treatment guidelines issued by the National Comprehensive Cancer Network (NCCN) recommend QRT-PCR testing to measure bcr-abl levels at diagnosis (before initiation of treatment) and every 3 months (during TKI treatment). When a patient reaches CCyR, bcr-abl levels should be measured every 3 to 6 months¹ Unlike cytogenetic testing, QRT-PCR can be performed on peripheral blood, without the necessity of obtaining from a bone marrow aspiration.¹

Studies have shown that the molecular response is associated with patient outcomes as early as 3 months after initiation of TKI treatment, and can provide important clinical insights in patients who are in CCyR:

Clinical significance of an increase in bcr-abl transcripts

Rising bcr-abl levels may indicate a loss of response; however, it is important to consider other possible causes, such as^6,7

*Defined as a 3-log reduction from a standard baseline, equivalent to a bcr-abl/bcr transcript ratio of 0.1%.⁵