This study tests if injecting the MMR vaccine (measles, mumps, rubella vaccine) directly into pancreatic tumors can shrink them. Pancreatic cancer is a type of cancer that starts in the pancreas, an organ that helps in digestion and blood sugar management. Some tumors can't be removed by surgery, and those are called unresectable. This study is for adults with these types of tumors that have not shrunk enough for surgery after standard chemotherapy and radiation. The vaccine will be injected using a special tool to see if it is safe and can help make the tumors smaller.

• Participants must have pancreatic cancer that can't be removed by surgery.
• The study involves getting an injection directly into the tumor.
• It's important that participants haven't had a live vaccine or other cancer treatments recently.