New Assay Detects Persistent Disease in Leukemia Patients Thought to Be in Remission
The outcomes of chronic myeloid leukemia (CML) have dramatically improved as the result of tyrosine kinase inhibitor treatment. Use of a tyrosine kinase inhibitor regimen can lower the blood CML biomarker to levels imperceptible by current detection methods. For patients in “molecular remission,” however, uncertainties remain regarding whether they will relapse or if treatment should be discontinued. A study by Alikian et al in The Journal of Molecular Diagnostics describes a new personalized DNA-based digital assay that detects persistent disease in 81% of samples taken from a group of patients thought to be in remission.
“If validated in clinical trials of stopping [tyrosine kinase inhibitors], this technique 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approach to recommendations for dose reduction or drug cessation in individual patients, ensuring that therapy is withdrawn only from patients with the highest chance of long-term remission,” explained Jane F. Apperley, MD, PhD, FRCPath, of the Centre for Haematology, Imperial College London. Indeed, studies have shown that 60% of CML patients who achieve sustained undetectable levels of BCR-ABL1 transcripts—the hallmark biomarker of CML—experience disease recurrence after tyrosine kinase inhibitor treatment is withdrawn.
Study Findings
Investigators compared the sensitivity of the new technique, DNA-based digital polymerase chain reaction (PCR) assay, to three other quantitative PCR methods currently used to measure residual CML, including reverse transcriptase–quantitative PCR, quantitative PCR, and reverse transcriptase–digital PCR. RT-qPCR is currently the most widely used method for monitoring residual disease in CML patients.
Thirty-six samples were taken from six patients with early CML who were thought to be in deep molecular remission, as indicated by reverse transcriptase–quantitative PCR results. Repeat analysis using digital PCR with preamplification detected persistent disease in 81% of the samples. In comparison, the detection rate was 25% using reverse transcriptase–digital PCR and 19% for quantitative PCR. “We conclude that [digital PCR] for BCR-ABL1 DNA is the most sensitive available method of residual disease detection in CML and may prove useful in the management of [tyrosine kinase inhibitor] withdrawal,” stated Dr. Apperley.
The new assay has the potential to dramatically impact CML management. 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 reverse transcriptase–quantitative PCR until reaching molecular remission. At that point, routine monitoring would be augmented with digital PCR, allowing better-informed treatment decisions and improved patient management.
According to Dr. Apperley, the new method improves on previous methodologies in two key areas. First, digital PCR 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 second advancement afforded by the new method relates to the greater sensitivity provided by the digital PCR platform.
“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,” concluded Dr. Apperley.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
