Optimal radiotherapy planning and delivery is essential for irradiation of gastro-oesophageal junction tumors. There is a need for individualized radiotherapy delivery to the upper abdomen, because of mobility. Likewise, controlling gastric filling by instructing patients about fluid and food intake before treatment, may contribute to positional reproducibility. There is evidence that missing microscopic disease in treating the clinical target volume (CTV) results in a worse prognostic outcome. The investigators want to evaluate wether positional difference of stomach, with and without fasting prescription, has an impact of the delivered dose. They will focus on the part of the CTV extending in the stomach. The investigators hypothesize that measurement of the dose using verification kilovoltage cone beam CTs will provide information on potential cold/hot spots of dose delivery and monitor potential geometric differences during treatment. This may result in a suboptimal treatment and a reconsideration of matching target volume on soft tissue instead of bony landmarks. The investigators will evaluate the first clinical results with DGRT in patients with esophageal cancer.