1. Department of Oncology, University College London Hospitals, 250 Euston Road, London, NW1 2PG, UK
2. UCL Cancer Institute, University College London, 72 Huntley Street, London, WC1E 6DD, UK
3. Department of Neurosurgery, National Hospital for Neurology & Neurosurgery, Queen Square, London, WC1N 3BG, UK