Anal cancer is usually caused by HPV which is often transmitted by anal intercourse. This virus is extremely common- it is the most common sexually transmitted virus. HPV induced anal cancer and dysplasias consist a significant health issue in gay and bisexual men, especially in HIV-positive gay. The frequency of anal HPV infection in gay is fairly high (60%). HPV infects anus during anal intercourse, touching or sexual games, but can be also transferred from the penis (genitalia) during cleansing. Full anal intercourse is not essential for contracting HPV. In contrast with HIV contracting, condom cannot adequately prevent HPV infection. If HIV-positive gay, the frequency of HPV infection is high (90%) because of immunodeficiency and subsequent obstruction in virus clearance. In these populations, progression of HPV infection to anal cancer is easier because of the deficient host defense. In any case, in HIV-seropositive antiretroviral drugs do not reduce the frequency of dysplasias or anal cancer.
The major risk factors for developing anal cancer are warts and HPV infection, HIV infection, immunosuppression, long-term steroid use, low CD4 count (in the past) in HIV-seropositive, smoking, multiple sexual partners and limited use of condoms.
Anal cancer frequency in gay is 20 times greater than the general population. Approximately 50% of HIV-positive gay will have anal pre-malignant dysplasia and 10% of HIV-positive present with anal cancer.
HPV vaccines are given in young people for protection from HPV infection, especially with HPV types that are implicated in cervical cancer or cancers of vulva, vagina, anus, mouth and tonsils. These vaccines additionally protect from HPV types that cause most genital warts. Three vaccines are approved by FDA for HPV prevention. The recent 9-valent vaccine provides protection against the majority of HPV types that are implicated in genital warts. Moreover, the 9-valent vaccine prevents most cervical cancers and significantly reduces the incidence of other HPV-associated cancers.
The current HPV vaccines are based on HPV surface components. They contain recombined viral proteins without any part of DNA and they are not infectious. These proteins mimic the natural infection and stimulate immune system to develop adaptive immunity to HPV.
HPV vaccination must begin at the age of 12 through 26. After 26 years, vaccination is recommended in anal intercourse, immunosuppression or possible HIV-infection. Nowadays indications arise that HPV vaccine can help in the regression of already established HPV infection, warts or dysplasias.