over the dorsal and ventral axes. Values of D99% for all shifts over the dorsal-ventral and cranial-caudal axes averaged over all patients. The X-axis represents tumor displacement in the dorsal-ventral direction and the Y-axis the cranial-caudal direction. There is no shift in the left-right axis in this case. The dose increases when the tumor moves in the caudal and ventral direction. The dose decreases when the tumor moves in the cranial and dorsal direction.