Jean-Pascal Machiels, MD, PhD, from the Cliniques Universitaires Saint-Luc, Brussels, Belgium discusses the KEYNOTE-040 study (NCT02252042), a Phase III clinical trial which assessed the efficacy of pembrolizumab versus standard treatment for recurrent or metastatic head and neck cancer. Dr Machiels explains the results and gives his opinion on why they may not be telling us the whole story. This interview was recorded at the 2017 European Society for Medical Oncology (ESMO) conference held in Madrid, Spain.