JCO PO Article Insights: Analytical Validation of Tumor-Informed ctDNA Assays for MRD

In this JCO PO Article Insights episode, host Jordan Goldstein summarizes the article, "Generic Protocols for Analytical Validation of Tumor-Informed Circulating Tumor DNA Assays for Molecular Residual Disease: The Blood Profiling Atlas in Cancer's Molecular Residual Disease Analytical Validation Working Group Consensus Recommendation" by Baden et al. TRANSCRIPT Jordan Goldstein: Hello, and welcome to JCO Precision Oncology Article Insights. I'm your host, Jordan Goldstein from Stanford University. Today we're discussing a consensus recommendation published in JCO Precision Oncology titled "Generic Protocols for Analytical Validation of Tumor-Informed Circulating Tumor DNA Assays for Molecular Residual Disease" by lead author Jonathan Baden, senior author Lauren Leiman, and colleagues on behalf of the BLOODPAC Consortium. The liquid biopsy space is one of the most exciting frontiers in oncology right now, with rapid development and many potential uses. However, the field has really lacked a shared framework for how these assays should actually be validated. This paper attempts to solve part of that problem. Before going further, I want to mention that BLOODPAC stands for Blood Profiling Atlas in Cancer Consortium. This was developed in 2016 with the goal of accelerating liquid biopsy development through shared standards. It includes the leading cancer diagnostics companies alongside academics, pharmaceutical companies, not for profits, and regulatory agencies. So, what actually is ctDNA MRD, and why does it matter? ctDNA is short for circulating tumor DNA, which is DNA shed by tumors into the bloodstream and can be detected by genomic profiling of a simple blood draw. Compared to tissue biopsies, it's minimally invasive, easily accessible, and can reflect the genetic diversity of the entire tumor across anatomic sites. This can allow for comprehensive genomic profiling, identifying target mutations, and understanding anatomic heterogeneity prior to treatment. It also allows for repeated sampling during and after treatment to explore evolutionary dynamics and, most promisingly, to detect molecular residual disease or MRD, which is what we focus on in this article. MRD is the presence of tumor-derived DNA in blood following therapy at levels below the threshold of conventional imaging or standard pathologic assessment. Accurate MRD detection can transform therapeutic strategies, enabling more precise risk-adapted approaches. But detecting MRD is not simple. There's often a very small amount of tumor DNA in plasma after treatment, even going below one part per million or 0.0001% of the total circulating DNA, most of which is healthy, normal, cell-free DNA. Detecting a signal that faint, reliably and reproducibly, is quite technically demanding. Tumor-informed ctDNA assays address this by first sequencing the patient's primary tumor to identify somatic variants that are unique to that cancer. A personalized panel is then constructed to track those exact variants in serial blood samples. This allows greater sensitivity. However, the methods and protocols for pre-analytical, analytical, and clinical validation for tumor-informed MRD assays can vary greatly. This presents major challenges for regulatory approval and clinical implementation. With these consensus recommendations in this article, BLOODPAC focuses on developing a standardized framework for the analytical validation of any tumor-informed ctDNA MRD assay. Analytical validation ensures these assays are in fact measuring what they claim to measure with defined performance characteristics. BLOODPAC intentionally set out to keep their protocols as generic as possible with the only requirements being intended uses of the assay for: one, patients with cancer who have undergone curative-intent therapy; and two, for prognosis, treatment efficacy, detection of residual disease or recurrence, or serving as the basis for a novel clinical trial strategy. With the goal of accele