[1] Northern Ctr Canc Care, Newcastle Upon Tyne, Tyne & Wear, England
[2] MRC, Clin Trials Unit, London, England
[3] Univ Oxford, Gray Inst Radiat Oncol & Biol, Oxford, England
[4] Cardiff Univ, Cardiff CF10 3AX, S Glam, Wales
[5] Imperial Coll Healthcare NHS Trust, London, England
[6] Cardiff Univ, Sch Med, Cardiff, S Glam, Wales