I don`t know about Cancer, but I don`t feed them because they are a risk for Aflatoxin. This is a mold which grows in the soil and peanuts are grown in soil. Aflatoxicosis is a bad fungus infection in all the airsacks of the birds, and usually fatal, although I have heard recently that they are better able to treat it. But why chance it. I feed Almonds in the Shell instead. Of course these have to be washed in hot water first, cause sometimes they are kind of dirty.