All I know is that obesity and doing it in the butt have exploded since 1995. The answer is probably in there somewhere. BTW, for clarity, I do not believe this has anything to do with people we all know who were diagnosed with this cancer in years past. I think what we’re seeing is a new demographic that has found a new way to acquire a disease.
Rectal cancer is what you see as a STD. Colon cancer, unless someone has a nine foot schlong is not due to sexual fluids.
You just don’t know if “ doing it in the butt have exploded since 1995” has really increased. People are not going to talk about sexual behavior in a questionnaire.