[1] Maastricht Univ, Med Ctr, Dept Radiat Oncol MAASTRO, Maastricht, Netherlands
[2] Int Network Canc Treatment & Res, Oxford, England
[3] Univ Oxford, Gray Inst Radiat Oncol & Biol, Oxford OX1 2JD, England
[4] Inst Canc Res, Sutton, Surrey, England
[5] Univ Dundee, Dept Radiotherapy, Dundee DD1 4HN, Scotland