This study investigates the use of stereotactic body radiation therapy (SBRT) for treating pancreatic cancer. Pancreatic cancer, including cancer of the ampulla of Vater, is a type of cancer that affects the pancreas, an organ behind the stomach that helps with digestion. This study focuses on patients whose cancer cannot be removed by surgery, is close to being removable, or has come back after treatment.

Participants in this study will receive SBRT, a type of radiation therapy that targets tumors with high precision. This therapy aims to deliver radiation to the cancer cells while minimizing damage to nearby healthy tissue. Patients will be monitored for safety and any side effects related to the treatment.

• Who can participate: Adults with confirmed adenocarcinoma (a type of cancer) of the pancreas or ampulla of Vater, with tumors less than 8 cm, may participate. Participants should have completed prior treatments like chemotherapy or surgery at least 180 days ago. Acceptable organ function and a life expectancy greater than 3 months are required.
• Study details: Participants will undergo stereotactic body radiation therapy (SBRT). This involves precise targeting of the tumor with radiation. Participants must have radio-opaque markers (markers visible on X-rays) within the tumor bed to aid in treatment accuracy.