Multinational, randomized, controlled, open-label, multicenter phase II trial. Eligible patients will be randomized in a ratio of 1:1 to Experimental Arm (FDG-PET-based small volume accelerated radiotherapy with concurrent standard of care chemotherapy) or Conventional Arm (standard FDG-PET-based radiotherapy with concurrent standard of care chemotherapy). Patients showing complete response, partial response, or stable disease following chemoradiotherapy will receive standard of care consolidation therapy with durvalumab (fixed dose of 1500 mg q4w) for up to 12 months or until progression of disease, unacceptable toxicity, patient´s wish, or investigator´s decision, whichever comes first.

After end of durvalumab therapy, patients will undergo safety follow up for 90 (+7) days followed by survival follow up until overall end of study. Overall end of study will be reached 24 months after the last patient has started durvalumab therapy. Patients showing PD following chemoradiotherapy will be treated according to investigator´s decision but will be followed up until overall end of study.