A study testing the routine use of ultrasound measurements when selecting the electron energy for breast boost radiotherapy

The determination of the depth of the tumour bed within the breast requirin g an electron therapy boost dose is generally judged clinically and can be inconsistent between individual radiotherapists. High frequency ultrasound provides a reproducible, safe and quick method of measuring this depth. In order to improve current working practice at the Royal Marsden NHS Trust th e routine use of ultrasound when planning breast boost radiotherapy was est ablished. Fifty-three early stage postoperative breast cancer patients had both clinical and ultrasound assessments of boost depth performed. These me asurements were converted into electron energy and compared. Measurements r anged from 0.8 cm to 4.9 cm and electron energy from 4 MeV to 15 MeV. As a direct result of the ultrasound measurements taken, 60% of patients had the ir electron energy changed from that chosen by the clinically assessed meas urement. Overall, the energy was as likely to be increased as decreased. Br east size did not influence the need for change but patients with small bre asts never required an increase in the energy from that chosen clinically. It was concluded that the use of ultrasound, once integrated into the plann ing process, can improve accuracy when selecting electron energy for patien ts receiving breast boost irradiation.