Researchers presenting at ESTRO 2026 reported a new approach to guide treatment in advanced cancer using circulating tumor DNA (ctDNA) detected in blood plasma. The work positions ctDNA as a tailoring biomarker for patients with oligometastatic disease, with the presentation emphasizing the potential to connect molecular signals from blood to therapeutic decision-making. In this framework, ctDNA functions as a real-time or near-real-time proxy for tumor burden and treatment response, potentially supporting earlier treatment adjustments than imaging alone. For the oncology pipeline, the key implication is continued investment in liquid biopsy readouts that can accelerate stratification and strengthen evidence packages for targeted or adaptive radiotherapy strategies.