How reliable is deep inspiration breath hold at CT simulation? Clinical impact of surface-guided breathing training in breast cancer radiotherapy.

Abstract

Deep inspiration breath hold (DIBH) is widely used to reduce cardiac dose in left-sided breast radiotherapy. However, the reliability of DIBH at CT simulation, has not been systematically evaluated despite the importance of CT simulation as the basis for treatment planning. We investigated the clinical impact of surface-guided breathing training on DIBH reliability and cardiac dose sparing. In this retrospective cohort study, 115 breast cancer patients undergoing DIBH CT simulation were analyzed before and after implementation of surface-guided breathing training using an SGRT system. DIBH performance was quantified by partial lung volume increase (PLVI) and breath-hold variability. Correlations between external surface motion and internal DIBH depth were assessed. Cardiac dose metrics were compared, with a subgroup analysis for patients receiving lymphatic drainage area (LDA) irradiation. Prior to training, insufficient DIBH CTs-including negative PLVI cases-were observed. After training implementation, all CT scans were acquired in intended breath-hold states, eliminating insufficient DIBH acquisitions. Mean PLVI increased by ~ 9%, and breath-hold variability decreased by ~ 26%. Sternum motion correlated most strongly with PLVI, with multiregion surface monitoring yielding the highest internal correlation. These improvements were reflected in significant reductions in cardiac dose, particularly in the LDA subgroup, with selected heart dose metrics reduced up to 96%, while maintaining target coverage. DIBH at CT simulation with surface-guided breathing training proves to be reliable. The training prevents planning CTs in wrong breathing states and thus enables clinically meaningful cardiac dose reduction in breast radiotherapy.