The optimal daily intake of vitamin D is not known, although many believe it should be higher than it is for most people living in sun deprived countries.
However, data analysis of nine case-control studies from the International Pancreatic Cancer Case-Control Consortium seem to show a small association between pancreatic cancer risk and increasing dietary vitamin D intake.
Remember, though, that data trawls like this are prone to confounding.
Waterhouse, M. Risch, H.A., Bosetti, C., Anderson, K.E., Petersen, G.M., Bamlet, W.R., Cotterchio, M., Cleary, S.P., Ibiebele, T., La Vecchia, C., Skinner, H., Strayer, L., Bracci, P.M., Maisonneuve, P., Bas Bueno-de-Mesquita, H., Zatoński, W., Lu, L., Yu, H., Janik-Koncewicz, K., Neale, R.E., for the Pancreatic Cancer Case-Control Consortium (PanC4). (2015) Vitamin D and Pancreatic Cancer: A Pooled Analysis from the Pancreatic Cancer Case-Control Consortium. Annals of Oncology. First published online: May 14, 2015. doi: 10.1093/annonc/mdv236.