[1] Northern Ireland Canc Ctr, Belfast, North Ireland
[2] Univ Coll London Hosp NHS Fdn Trust, London, England
[3] Royal Marsden Hosp NHS Fdn Trust, London, England
[4] Inst Canc Res, London, England
[5] Radiotherapy Trials Qual Assurance RTTQA Grp, Northwood, England