There are quite a number of reports of Vietnam Vets dying of this problem. In some cases it appears to be attributed to some form of parasite or liver fluke (I believe?). But if you google 'Cholangiocarcinoma in Vietnam Vets' I think you're going to find a 'load' of people who are seeking information and posting on the subject.
I'm not sure a lot of research has been done on this subject, but perhaps if all of the interested parties out there got together or organized, something might be done if someone could put together some statistics.
Sorry Dot, I called you Deb..............
I'm not sure if this will help since it's an older report and based on studies of Korean Vets, but it might be a starting point: http://www.dva.gov.au/media/publicat/2003/kwmortality/appendix_b.htm#B22. You could also query about helminthic infections - which might give you an overview of what happens when someone acquires a biliary 'liver' fluke and the advancement to serious problems.