Abstract
Tumor regression throughout treatment would induce organ movement, but little is known of this in the esophagus. To achieve successful tumor regression, radiation therapy requires several weeks of radiation to be delivered accurately to the tumor. Usually, a 5-10 mm margin is allowed for set-up error and internal organ motion. Our case exhibited an unexpectedly large movement of the esophagus across the aorta with tumor regression that extended outside the margin and thus outside the radiotherapy field. These movements may affect subsequent invasive procedures or treatment during cancer therapy. After the unexpected large movement of the esophagus due to tumor regression, we revised the radiotherapy plan to reflect the new esophageal position. This implied that regular imaging and close monitoring are required during treatment of esophageal cancer.