1 University College London, Division of Surgery and Interventional Science, London W1W 7EJ, UK. Electronic address: jayant.vaidya@ucl.ac.uk.
2 Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
3 Department of Biostatistics, University of Notre Dame, Fremantle, WA, Australia; Clinical Trials Group, Division of Surgery and Interventional Science, University College London, London, UK.
4 Department of Clinical Oncology, University College London Hospitals, London, UK.
5 Department of Radiation Oncology, Sir Charles Gairdner Hospital, Perth, WA, Australia.