Study of Interest of Personalized Radiotherapy Dose Redistribution in Patients With Stage III NSCLC

In patients with locally advanced stage III non-small cell lung cancer, the probability of local control remains low (about 17% at 1 year). Concomitant radio-chemotherapy is the standard treatment. An increase in total radiotherapy dose (from 66 to 74 Gray) has been proposed to improve local control, with contradictory results. Relevant FDG-PET scan images can be acquired during radio-chemotherapy, with a demonstrated prognostic impact and recently in a multicentre prospective study. A significant reduction in FDG uptake / volume (metabolic response) suggests that the radiotherapy target volume could be reduced during radiotherapy possibly improving organs at risk tolerance. Conversely, a lack of metabolic response may justify treatment intensification before the end of radiotherapy. The investigators hypothesis is to investigate the individual tumour heterogeneity on FDG-PET during radio-chemotherapy to reduce the volume to a biological target that could receive a higher total dose (personalized dose redistribution).