Improved chest wall stability during deep-inspiration breath-hold in breast cancer radiotherapy following quality improvement initiatives.

Intrafractional chest wall motion during radiotherapy in deep-inspiration breath-hold may compromise dose delivery to the internal mammary nodes in patients with breast cancer. The present study evaluated chest wall motion after implementation of four treatment quality improvement initiatives, including repositioning of the gating marker block from the upper abdomen to the chest wall. Geometrical errors were quantified using cine MV images. The occurrence of geometrical errors >3 mm was 4.7%, which was significantly lower than before the improvement initiatives (21.2%, p < 0.0001). However, predominantly mild skin-related side effects were reported by 61% of patients caused by the gating marker block overlapping with the treatment field.