Explain the process of how smoking can lead to pancreatic cancer. How can this habit destroy the pancreas?

We found out that Patrick Swayze, who recently died of this type of cancer last night, was a smoker. Regrettably, he did not completely quit. Of course, cigarette smoke has a lot of lung-damaging chemicals, such as benzene and CO, but what is the one thing in this smoke which can can wreak havoc with the pancreas?