This is an open, multinational, phase 2 trial to investigate the Properties of cancer cells before, during and after treatment with the investigational study drug durvalumab in patients with locally advanced non-small celled lung cancer (NSCLC). Both patients with high and low PD-L1 expression are allowed to participate. Durvalumab (PD-L1 inhibitor) will be administered after a period with standardtreatment with chemotherapy and radiationtherapy (chemoradiotherapy) for around 7 weeks. After maximum 5 weeks break after chemoradiotherapy, durvalumab will be given in the same dose to all patients for up to 12 months. The follow-up include a safety follow-up for up to five years, followed by a survival follow-up for up to a total of ten years.

The main aim is to identify and describe biomarkers in different sample types related to chemoradiation followed by durvalumab treatment for stage III PD-L1 negative and positive non-small cell lung cancer (NSCLC) patients' eligible for curatively intended chemoradiation.

The hypothesis is that clinical differences in course of disease reflect underlying biological characteristics.