Researchers built a standardized rulebook for a key clinical milestone—time to subsequent therapy (TTST)—aimed at helping oncology trials and clinicians decide when patients should move off a failing regimen. The framework addresses how to define TTST consistently across studies, improving comparability when therapies are adjusted. In modern cancer development, time-to-next-treatment is often treated as a practical proxy for clinical deterioration, but inconsistent definitions can confound interpretation. A clearer scoring approach can improve endpoint reliability for regulators and sponsors. The work is poised to influence trial protocol design, especially for studies where multiple lines of therapy and rapid crossover complicate endpoint measurement.