A phase II proof of concept, multi-centre, safety and efficacy study with a biomarker component to investigate if a treatment strategy where stereotactic body radiation therapy (SBRT) is given with pembrolizumab is sufficiently active to warrant further investigation in randomized phase II or III studies. The study will run for approximately 3 years, including 2 year of recruitment and 1 year of follow up. There will be two study arms. Enrollment of 15 patients into arm A will occur before the start of enrollment of the next 20 patients on arm B.