David Pinato, MD, MRes, PhD, Imperial College London, London, UK, outlines the impact of host determinants on response to immunotherapy in patients with non-small cell lung cancer (NSCLC), highlighting PD-L1 expression as a biomarker for pembrolizumab response. Dr Pinato also discusses the findings of a study which reported that antibiotic therapy has a significant negative impact on pembrolizumab monotherapy outcomes, but not on chemotherapy outcomes, in patients with NSCLC. This interview took place during the 19th British Thoracic Oncology Group (BTOG) Annual Conference 2021.