At ESTRO 2026, researchers presented approaches aimed at tailoring radiotherapy using circulating tumor DNA (ctDNA) and blood-based testing. The reported work describes a new blood test designed to detect tumor DNA to guide treatment in advanced cancer settings, with potential use cases in oligometastatic disease. The ctDNA approach is positioned as a pathway to align treatment intensity with measurable disease dynamics. If validated across cohorts, such testing could reduce uncertainty in who should receive radiotherapy escalation versus systemic management. Separately, other ESTRO 2026 presentations highlighted short-course and targeted radiotherapy scheduling strategies for prostate and early-stage breast cancer spread, suggesting growing momentum for more efficient, biology-informed radiation planning.