Brian O’Sullivan is a Professor in the Department of Radiation Oncology at the University of Toronto, Toronto, Ontario, Canada. He also holds the Bartley-Smith/Wharton Distinguished Chair in Radiation Oncology in the Department of Radiation Oncology at the Princess Margaret Hospital, University of Toronto. He received his medical degree from the National University of Ireland at University College in Dublin in 1976, and completed internship and general internal medicine at St. Vincent’s Hospital in Dublin. Additional postgraduate training includes a fellowship in medical oncology, and a residency and clinical fellowship in radiation oncology, all at Princess Margaret Hospital in Toronto, Canada. Professor O’Sullivan is the Head and Neck Oncology Program Chair at Princess Margaret Hospital and immediate past-Chair of the Head and Neck Oncology Committee of the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG). He is now the co-Chair of the US NCI Head and Neck Steering Committee, Coordinating Center for Clinical Trials, CTEP. He is the recipient of numerous international awards, and research grants. He has published almost 300 peer reviewed papers, in excess of 50 book chapters, and has written or edited 6 oncology textbooks. His interests includes sarcoma and head and neck cancer, translational research, IMRT delivery and the principles of image guided radiotherapy, chemo-radiotherapy and molecular targeting. He is a member of the TNM Committee of the Union for International Cancer Control (UICC), Chair of the UICC Prognostic Classification Sub-Committee and represents the UICC as head and neck cancer and sarcoma liaison to the American Joint Committee on Cancer (AJCC). He was elected to the ICRU in 2014.