Tracking Treatment Response: ctDNA Insights in MMR-p Colon Cancer

Host: Brian P. McDonough, MD, FAAFP Guest: Christopher T. Chen, MD What if a simple blood draw could reveal whether a patient is responding to treatment before surgery? That question is at the heart of a study presented at the 2025 ESMO Congress, which investigated neoadjuvant immune checkpoint blockade in mismatch-repair-proficient (MMR-p) colon cancer. In addition to confirming that combination immunotherapy prior to surgery is a safe and feasible approach, the study also found that circulating tumor DNA (ctDNA) levels correlated with both tumor burden and early treatment response. Joining Dr. Brian McDonough to unpack these insights is Dr. Christopher Chen, Assistant Professor in the Division of Oncology in the Department of Medicine at Stanford University School of Medicine.