MRD Testing: From Residual Disease to Real Decisions with Chris Hourigan and Gary Pestano

Molecular residual disease, or MRD, has been part of oncology’s vocabulary for decades. But knowing something is there and being able to measure it precisely are two very different things. In today’s show, we explore how MRD testing moved from a long-standing clinical suspicion to one of the most consequential tools in modern oncology.Joining us on the program are Chris Hourigan, Director of the Fralin Biomedical Research Institute Cancer Research Center (DC) at Virginia Tech, bringing the academic and clinical AML lens, and Gary Pestano, Chief Scientific Officer at Biodesix, offering the industry and diagnostic development perspective.Hourigan reminds us that MRD itself isn’t new. What was missing were the tools. From counting cells under a microscope to flow cytometry and now highly sensitive molecular techniques including droplet digital PCR, MRD has evolved into a quantitative, actionable signal. Coming from the side of commercializing and scaling assays, Pestano underscores the central challenge of distinguishing meaningful signal from background noise. “There is a lot circulating in our blood. The key is what is meaningful, what is not meaningful,” he explains. Sensitivity alone isn’t enough. Target selection, bioinformatic filtering, validation at scale, and real-world reproducibility all determine whether MRD can truly guide care. The field is very much still work in progress, say both.Looking ahead, they point toward quantification as the next frontier. MRD is no longer just about detecting what remains. It’s about deciding what happens next.“We’ve been talking about MRD as if it’s a binary concept” says Hourigan. “I can imagine in the future, there’s going to be windows, and we will tune therapy to what comes next.”Thank you to Bio-Rad for sponsoring today’s show. Bio-Rad is your trusted partner for absolute quantification and reproducible results in oncology research. Bio-Rad helps you move from data to confident decisions. Learn more at bio-rad.com/oncology. This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit www.mendelspod.com/subscribe