TROG 14.04 tested the feasibility of Deep Inhalation Breath Hold (DIBH) to reduce heart radiation dose in left sided breast cancer patients in a multicentre setting. Patient reported outcomes such as anxiety associated with holding their breath were also investigated in comparison to right-sided breast cancer patients treated in free breathing (normal breathing). The study confirmed that DIBH has the potential to reduce the radiation dose to the heart for left sidedbreast cancer patients receiving radiotherapy in a variety of settings. There was a slightly higher anxiety scores among DIBH patients suggest the act of breath holding, or knowledge of the purpose of DIBH, may increase patient anxiety. However, this increased anxiety reduced to levels similar to the control group of right sided breast cancer patients throughout the course of their treatment.