Standard operating procedure (SOP) for immobilisation, scanning, verification and treatment of breast cancer patients undergoing proton beam therapy

The use of proton beam therapy (PBT) for breast cancer is not currently included for standard consideration on the NHS England indication list. However, there are occasions where the use of PBT may be approved in the United Kingdom (UK), such as breast sarcoma, as part of a clinical trial or due to a photon plan meeting a threshold for significant risk of acute and late toxicities (e.g. pre-existing co-morbidities). Due to the beam characteristics, the use of PBT for breast treatment poses challenges in terms of the immobilisation, pre-treatment scanning, treatment verification and delivery. This standard operating procedure (SOP) details strategies to mitigate these that were developed as part of the implementation of breast PBT at our institution. This SOP will support existing and new PBT services when treating this patient cohort, by providing a detailed step-by-step guide to improve consistency and efficiency in the management of breast PBT.