Cancer prevention is a serious effort in many areas of medicine. As technology advances, we're learning more about the life-threatening disease, but what happens when a cancer stems from a sexually transmitted infection (STI)?

Human papillomavirus (HPV) is an STI known to cause cancer. HPV cancers can occur in multiple organs of the body, linking the virus to cervical, penile, anal, vaginal, and some throat cancers. The Centers for Disease Control and Prevention (CDC) estimates that more than 21,000 HPV-associated cancers occur in women and 12,000 HPV-associated cancers occur in men each year. As a result of such prevalence, a vaccine has been made against four of the 40 types of HPV that can infect those who are sexually active. The vaccine protects against contraction of two to four HPV types, depending on the vaccine and dosage taken. If individuals protect themselves from risky forms of HPV — through such vaccines — then they stand a better chance at preventing cancer. However, since their inception, these vaccines have been targeted to young girls and women, who are affected by the most types of HPV-associated cancers.

A new study now indicates that homosexual men are 15 times more likely to develop HPV-associated cancers than heterosexual men. These men become more likely to develop genital warts and anal cancers as a result of their HPV.

HPV vaccination in girls has had an impact on the prevalence of genital warts in heterosexual men, the authors explained, but there has been no such change in prevalence among gay men. HPV appears to affect all sexually active parties equally, though the researchers have found that anal cancers associated with HPV are more likely to develop in homosexual men, and even more so in HIV-positive homosexual men. Similarly, it is also difficult to prevent cancer in HIV-positive men with HPV, as their immune systems are compromised by their contraction of both STIs, not necessarily just the HPV.

The study administered the HPV vaccine to Australian boys 12 to 15 years old. The researchers found that these boys developed a sort of HPV immunity, as the girls did when they were vaccinated. The positive result was seen especially in those who were not sexually active and had no prior exposure to HPV. This caveat is favorable, as the study also indicated that only five percent of homosexual men under the age of 25 are exposed to high-risk and cancer-causing HPV, while 10 percent of their counterparts between the ages of 25 and 44 are exposed. As a result of vaccination, likelihood of infection with dangerous forms of HPV dropped to a manageable range of less than five percent.

While the dearth of HPV infection in this population of men may call for an argument regarding cost-efficacy of vaccinating males, it is important to realize the importance of cancer prevention. The HPV vaccine provides homosexual men with an avenue of protection and prevention that only heterosexual men are offered at this point. In many countries, only women are vaccinated, as a means to prevent the STI in men. But this strategy misses major considerations by assuming only heterosexual relationships as a factor. Vaccination of boys also confers their protection against dangerous HPV-related cancers, regardless of their sexual orientation. As a result, the vaccine can be used to save many more lives.

"In the light of this evidence, and in the absence of universal vaccination of boys, the argument for introducing targeted HPV vaccination for [homosexual men] up to age 26 years is strong," concluded the authors.

Source: Lawton MD, Nathan M, Asboe D. HPV vaccination to prevent anal cancer in men who have sex with men. Sexually Transmitted Infections. 2013.