These studies aren't very useful without considering the base rate. From Google, the lifetime risk for men for pancreatic cancer is about 1.8% (1.7% for women). the article said vegetarians had 21% less chance, which means it's a 1.4% chance.
To me this smells like a study with a lot of data massaging to get something publishable.
Logistics has always been the main factor in winning wars.