A randomised, two-arm, non-blinded crossover study investigating the impact of treatment position (prone versus supine) upon reproducibility of tumour bed position in patients undergoing breast radiotherapy following excision of early breast cancer.

To establish whether or not the prone (face down) position reduces exposure of healthy tissue to radiation when compared to the supine position. To compare patient comfort and acceptability in each of the prone and supine positions. To perform a time and motion study for radiotherapy planned and delivered in each of the prone and supine positions.

Inclusion Criteria:

• Complete microscopic excision of early stage invasive ductal or lobular carcinoma (pT1-3b N0-1 M0) with breast preservation.
• Paired titanium clips marking anterior, posterior, and radial walls of excision cavity
• Breast cup size C or above
• Recommendation for whole breast radiotherapy
• No requirement for nodal irradiation
• Ability to lie prone on breast board
• For left-sided breast cancer patients, cardiac and LAD doses must be ≤10% greater than those predicted for the supine position.
• For all patients, the following absolute dose constraints should be met: ≤5% of heart volume to receive 18Gy and ≤10% of ipsilateral lung volume to receive ≥20Gy
• Age ≥18
• PS ≤1
• No previous radiotherapy to the affected breast
• No concomitant herceptin
• Absence of any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule.
• Written informed consent given according to ICH/GCP before registration/ randomisation.
• Patients can only be randomised into this trial once.