Motive: In order to improve the treatment technique, a comprehensive follow-up program is needed to obtain all relevant patient, treatment and toxicity data from esophageal cancer patients. Goal: To set-up and maintain a database containing treatment results in terms of tumor control, side effects, complications and patient-reported quality of life. A standard database of patients receiving photon treatment will be created. These data are then linked to dose-volume data of radiotherapy, with the aim to build prediction models for both tumor control and toxicity after radio (chemo) therapy that can later be used for selecting patients for proton treatment.