Currently, patients of suitable fitness with non-metastatic esophageal cancer are treated with surgery, radiotherapy or chemoradiotherapy. If treated with radio or chemoradiotherapy, a Computerised tomography (CT) scan is performed and is the dataset used for planning radiotherapy. Information from the endoscopic ultrasound (EUS), performed during routine staging, is used to help localize the tumor, as tumors of the esophagus are poorly visualised on CT. This information is subjective and dependant on the clinician performing the procedure. The tumor is described in relation to common anatomical landmarks. Interpretion of this information can lead to over-compensation when attempting to cover the tumor with a radiation field, to avoid a "miss". It is thought that using fiducial markers called Visicoils placed in or adjacent to the tumor's top and bottom extent at the time of EUS, will lead to better definition of the tumor in the planning process and hence, improvement in local tumor control, and reduction in radiotherapy dose to normal tissue.