 Metabolic and Molecular Response evaluation for the individualization of therapy in adenocarcinomas of the gastroesophageal junction by evaluation of the R0 resection rate for patients with metabolically ie, according to PET criteria chemotherapy-resistant locally advanced AEG, who receive an intensified neoadjuvant chemoradiotherapy INRCT. Additonal efforts will be done by investigation of molecular and metabolic biomarkers in relation to their predictive and prognostic value by correlating them with histopathologic responses and clinical outcome in an exploratory approach. 