This study investigates the Breathe Well device to test whether it is superior to the existing treatment standard of the Varian Realtime Position Management (RPM) system in assisting patients with deep inspiration breath hold.

Recent studies have demonstrated an increased risks of cardiac disease in breast cancer radiotherapy patients. For patients diagnosed <50 years old, the risks for cardiovascular diseases/events were increased by 24-82% comparing left and right breast radiotherapy. The deep inspiration breath hold (DIBH) technique addresses this problem by reducing the heart dose by up to half, thus potentially reducing the increased rate of major coronary events by 20%. Providing patients with visual feedback in addition to audio guidance has been demonstrated to improve the reproducibility of the DIBH technique by 95% and stability by 80%.

Breathe Well is a new audiovisual feedback device that may increase the accuracy and workflow of implementing DIBH for breast cancer patients.

Inclusion Criteria:

• Left-sided breast cancer patients (invasive and in situ)
• Supine positioning of the patients.
• Ability to perform a ≥20s breath hold
• >18 years old
• An ECOG score in the range of 0 to 2
• Able to give written informed consent and willingness to participate and comply with the study
• Patients must be able to read and complete questionnaires in English

Exclusion Criteria:

• Involvement or at risk regional lymph nodes
• Pregnant / lactating women

Anonymised data will be made available to researchers upon request, once evidence of ethical approval has been provided.