Navigating Variability in Prostate RT Planning: Real-Time Insights for Human-Centered CDS Design

Clinical variability in prostate radiation therapy (RT) planning is well documented, but little is known about how radiation oncologists experience and adapt to the factors that drive it. This study explores variability as a human-centered design challenge, with the goalofinformingclinicaldecision support (CDS) design through real-timeinsight into planning decisions. We conducted observation sessions with the think aloud method followed by semi-structured interviews with five radiation oncologists while they contoured prostate cases. Using the Systems Engineering Initiative for Patient Safety (SEIPS) framework, we thematically analyzed the contributors to variability across tasks, technology, and organizational conditions. Results suggest that variability arises not only from anatomical or guidelineambiguity, butalso fromindividual interpretations of inputs, variation in contouring decisions, andadaptive strategies such as reliance on prior experience and estimation under uncertainty. Findings support the design of context-sensitive CDS tools that reflect real-world clinical reasoning while preserving clinical flexibility.