Interferon is actually used in some cancer treatments such as hairy cell leukemia, kidney cancer and melanoma. Ribavirin can cause tetragenic effects in animals. You are worrying needlessly about that.
Here's a link, it shows most of everything. cheers!!
http://www.pegasys.com/patient/index.html
No. Cancers are not caused by hepatitis C treatment drugs including interferon.
But if you have had cancer before, it is a good idea if you check with your oncologist. Especially if you are taking drugs for your cancer. You should want to make sure that there is no interaction between the drugs.
Good luck.
Hector