As explained here by James Spicer, PhD, FRCP, of Guy’s and St Thomas’ NHS Foundation Trust, London, UK, the field of lung cancer research is currently dominated by immunotherapy. Prof. Spicer highlights the need for predictive biomarkers, such as tumor mutational burden (TMB), to determine response to these agents and how this is more complex than it seems. This video was recorded at the British Thoracic Oncology Group (BTOG) Annual Conference 2018, held in Dublin, Ireland.