1. Health Economics Research Centre, Nuffield Department of Population Health, University of Oxford, Old Road Campus, Headington, Oxford, Oxfordshire, OX3 7LF, UK.
2. Health Economics Research Centre, Nuffield Department of Population Health, University of Oxford, Old Road Campus, Headington, Oxford, Oxfordshire, OX3 7LF, UK
3. Oxford Cancer & Haematology Centre, Churchill Hospital, Oxford, Oxfordshire, OX3 7LE, UK