A new assay is more accurate than the current gold standard for detecting residual disease in patients with chronic myeloid leukemia (CML), according to a study published in The Journal of Molecular Diagnostics.
Investigators found this test, a DNA-based digital PCR (dPCR) assay, could detect persistent disease in 81% of samples taken from CML patients who were in remission according to reverse transcriptase-quantitative PCR (RT-qPCR).
RT-qPCR is currently the most widely used method for monitoring residual disease in CML patients.
“If validated in clinical trials of stopping TKIs [tyrosine kinase inhibitors], this technique [the dPCR assay] will permit a more personalized approach to recommendations for dose reduction or drug cessation in individual patients, ensuring that therapy is withdrawn only from patients with the highest chance of long-term remission,” said investigator Jane F. Apperley, MD, PhD, of Imperial College London in the UK.
For this study, Dr Apperley and her colleagues compared the sensitivity of the dPCR assay to 3 other quantitative PCR methods currently used to measure residual CML—RT-qPCR, quantitative PCR (qPCR), and reverse transcriptase-digital PCR (RT-dPCR).
Thirty-six samples were taken from 6 patients with early CML who were thought to be in deep molecular remission, as indicated by RT-qPCR results.
Repeat analysis using dPCR with preamplification detected persistent disease in 81% of the samples. In comparison, the detection rate was 25% using RT-dPCR and 19% for qPCR.
“We conclude that dPCR for BCR-ABL1 DNA is the most sensitive available method of residual disease detection in CML and may prove useful in the management of TKI withdrawal,” Dr Apperley said.
She and her colleagues believe the new assay has the potential to dramatically impact CML management. They foresee that, immediately after CML diagnosis, the patient’s genomic breakpoints would be identified, enabling the design of a patient-specific assay.
The patient’s response to therapy would be monitored using standard RT-qPCR until reaching molecular remission. At that point, routine monitoring would be augmented with dPCR, allowing better-informed treatment decisions and improved patient management.
According to Dr Apperley, the new method improves on previous methodologies in 2 key areas. First, the dPCR platform provides greater sensitivity.
And second, dPCR is a DNA-based method that allows identification of BCR-ABL1 fusion junctions by targeted next-generation sequencing. This enables the rapid generation of high-performing DNA-based hydrolysis probe assays that are specific to the individual molecular footprint of each patient’s CML clone, although the number and location of fusion junctions may vary among patients.
“The technique we describe, with which we successfully mapped a disease-specific junction in all patients tested, is relatively simple, cost-effective, and suited to a high-throughput laboratory,” Dr Apperley concluded.
