The investigators group uses an individualised radiation dose approach in which the dose is escalated up to pre-defined tissue constraints (see below). The target dose to the tumor is 69Gy. However, this dose cannot be reached in approximately 30% of the patients, even with an IMRT (Intensity Modulated Radiotherapy) technique, because the MLD (Mean Lung Dose) constraint of 20Gy is reached at a TTD (Total Treatment Dose) below 69Gy. In this study, the investigators will adapt the treatment by performing a new (PET)-CT at day 12 during radiotherapy and in case of a decreased Planning Target Volume (PTV), the dose mey be increased.