18F-FSPG PET/CT as a Non-Invasive Imaging Biomarker for Treatment Response to Chemoradiation in Esophageal Cancer

This study is testing a new PET/CT imaging scan using a tracer called 18F-FSPG to see if it can reliably measure how well chemoradiation (combined chemotherapy and radiation) is working in patients with locally advanced esophageal cancer. If the scan can detect early treatment response, doctors could better personalize treatment plans. **You may be eligible if...** - You are 18 years of age or older - You have been diagnosed with locally advanced esophageal cancer (tumor larger than 2 cm) - You are about to receive chemotherapy combined with radiation as your primary treatment - You are able to provide written informed consent - If you are a woman of childbearing age, you must have a negative pregnancy test before the scan **You may NOT be eligible if...** - You weigh more than 400 pounds or have a physical condition preventing imaging - You are pregnant or breastfeeding - You are allergic to intravenous contrast dye - You have already started treatment for this cancer Talk to your doctor to see if this trial is right for you.