That's funny this thread started 10 years back was refering to parasites as an hypothetical cause for cancer, and seeing all the current craze about an antiparasitic drug (Fenbendazole) which work wonder against all kind of cancers and tumors.
You guys were right about the parasite route.
Ivermectine, which is also a cheap antiparasitic drug, has strong effect to kill cancerous cells.
Parasites are also suspected to cause many other serious deseases, so I guess antiparasitic drugs should be the first drug one try when they are hit with this kind of deseases