Pancreatic cancer is one of the least looked at cancers in regards to vitamin D research. Furthermore, researchers are still looking at whether certain conditions respond better to vitamin D at specific and differing levels.
With breast cancer, an effect is usually only seen above 40 ng/ml and closer to 60 ng/ml. With diabetes, it is suggested that effects for vitamin D are only seen at levels of 32 ng/ml or higher.
So, with pancreatic cancer there is still a great amount of uncertainty. As with other conditions, vitamin D is not guaranteed to prevent or treat pancreatic cancer and it is not recommended to take vitamin D instead of any prescribed medicines.
As Rita touched on, work with a doctor if you have pancreatic cancer and wish to begin supplementing with vitamin D.