Professor O’Byrne is a Consultant and Professor in Medical Oncology, who recently moved to the Princess Alexandra Hospital (PAH) and the Queensland University of Technology (QUT) section of the Translational Research Institute (TRI) from St James's Hospital and Trinity College, Dublin. He has conducted translational 'bench-to-bedside-and back-again' research over the past 25 years with a focus on solid epithelial tumours, in particular in thoracic malignancies.

Prof O’Byrne has been involved in the design of and running phase I, II and III clinical trials encouraging the incorporation of biomarker studies, both prognostic and predictive, where possible. He has published over 250 manuscripts in peer reviewed journals and books and has edited 2 books in thoracic oncology.

In 2013, Prof O’Byrne moved to Brisbane to take up a role as a member of the Australian Prostate Cancer Research Group establishing close links Professors Colleen Nelson and Judith Clements, and forging links with the prostate group in Vancouver, Canada.