What if Cancer in Pancreas is Not Primary?

Hello, Can anyone please explain if there is a major difference between primary pancreatic cancer, and cancer in the pancreas that has metastasized from the breast? I'm unsure if the information I'm reading about pancreatic cancer is only applicable if it is primary. More specifically, does anyone know if response to treatment, and survival expectations, are the same whether it is primary or secondary? Any information would be so greatly appreciated. Thank you so much and God Bless.