I knew oral sex can transmit hpv and therefore lead to throat cancer and therefore I always use a condom. I started doing this while working as an escort and will now forever do so. I have since become a medical professional and have worked with people who have developed it. A huge proportion of mouth and throat cancers are due to HPV infection, just as are most cervical cancers. If people are prepared to risk losing their tongue (and having it replaced if you are lucky with part of your thigh, or forearm - yes it stays hairy), ability to speak through laryngectomy and want to breath through a hole in their neck (tracheostomy) then that's their look out. Bear in mind that radiotherapy and chemotherapy will make your teeth and hair fall out, will kill your taste buds so you can't taste you food and will destroy your salivary glands so that you may have to eat pureed food for the rest of your live. Of course there is always thae worst case scenario where it spreads like wildfire, gets into you lymph nodes and kills you. Yeah that's so worth it - not!
HPV I think is systemic so it can stay in in your body for a while. I don't think there are specific ones to arses, cervixes or throats, but am not entirely sure - there are differing severities of the virus, obviously with the higher risk ones being worse. The virus gets into the cells of mucous membranes, changes the DNA in the nucleus, therefore causing abnormal cell growth and cancer.
There is now a vaccine given to young girls to prevent HPV, and therefore cervical cancer - I assume it also has protection against the effect it has on the throat. But as it isn't routinely given to men yet I guess the best protection is condoms.
I love condoms - the best thing ever invented!