A randomised open-label phase III trial of Reduced Frequency pembrolizumab immuNothErapy for first-line treatment of patients with advanced non-small cell lung cancer (NSCLC) utilising a novel multi-arm frequency-response optimisation design. 

 To determine the optimally reduced frequency of first line pembrolizumab for advanced NSCLC, REFINE-Lung will recruit 1750 patients who are progression free after six months of treatment and are otherwise planning to continue pembrolizumab therapy. Randomisation is evenly distributed between control (six-weekly pembroluzimab) or one of four frequency-reduced arms (nine, 12, 15 and 18-weekly).