[1] Royal Marsden Hosp, Dept Paediat Oncol, NHS Trust, Sutton SM2 5PT, Surrey, England
[2] Univ Leicester, UKCCSG, Dept Epidemiol & Publ Hlth, Leicester LE1 6TP, Leics, England
[3] Sheffield Childrens Hosp, NHS Trust, Sheffield S10 2TH, S Yorkshire, England
[4] Hosp Sick Children, London WC1N 3JH, England
[5] Christie Hosp NHS Trust, Acad Unit Paediat Oncol, Manchester M20 9BX, Lancs, England