1 NHS England National Clinical Lead Proton Beam Therapy, UK; St James's Institute of Oncology, Leeds Teaching Hospitals NHS Trust, Leeds, UK. Electronic address: Adrian.crellin@leedsth.nhs.uk.
2 University of Cambridge Department of Oncology, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, UK; NCRI Clinical and Translational Radiotherapy Research Working Group (CTRad), UK.