Oral cancers (oropharyngeal cancers) not related to smoking or drinking have reached near epidemic levels in America. Spread by oral sex, adult males are twice as much at risk as women. The human papillomavirus, or HPV, is the causal agent....
http://www.consumerreports.org/cro/2012/02/how-can-you-get-hpv/index.htm
Note: As today's teens mature, the incidence rates will skyrocket. Teens don't think of having oral sex as serious in any way.