Sanjay Popat, BSc MBBS FRCP PhD, from the Royal Marsden Hospital, London, UK, discusses the CheckMate 153 study (NCT02066636) at the European Society for Medical Oncology (ESMO) 2017 in Madrid, Spain. The study involved patients taking nivolumab for a year, before being randomised to either continue or discontinue treatment. The results of this trial were eagerly anticipated, because there is no current definitive length of treatment for nivolumab. The study found that there was a significant improvement in progression free survival for patients who continued nivolumab compared to those who didn’t. However, more mature overall survival data is needed to determine whether a longer duration of nivolumab is of benefit.