Anal cancer is a malignancy whose incidence has been rising. Approximately 90% of cases are caused by persistent infection with the Human Papillomavirus (HPV). This strong link to a common virus means anal cancer is highly preventable through proactive measures. Strategies for risk reduction include vaccination, lifestyle modifications, and early detection protocols.
Preventing HPV Infection
The primary approach to preventing anal cancer centers on stopping the infection that causes it, which is achieved most effectively through vaccination. The 9-valent HPV vaccine, known as Gardasil 9, protects against the types of HPV responsible for nearly all anal cancer cases, specifically types 16 and 18. Routine vaccination is recommended for children at age 11 or 12, though the series can begin as early as age nine.
Catch-up vaccination is recommended through age 26 for anyone who was not adequately vaccinated when younger. For adults aged 27 through 45, vaccination is not routinely recommended, but a discussion with a healthcare provider may lead to a shared clinical decision to proceed. This later vaccination is less effective because the individual may have already been exposed to some HPV types, but it can still offer protection against types not yet acquired.
HPV is transmitted through skin-to-skin contact, often during sexual activity. Barrier methods, such as condoms and dental dams, can reduce the risk of transmission, but they do not offer complete protection. This is because the virus can be present on skin areas not covered by the barrier. Limiting the number of lifetime sexual partners can also decrease the likelihood of encountering a persistent HPV strain.
Modifying Lifestyle Risk Factors
While HPV infection is the precursor for most anal cancers, certain conditions increase the risk that the infection will progress. Smoking is a modifiable risk factor, as tobacco toxins weaken the local immune response in the anal area. People who currently smoke are more likely to develop anal cancer compared to non-smokers, even when controlling for HPV status. Quitting smoking can help reduce the overall risk.
A weakened immune system, or immunosuppression, is a substantial risk factor because it impairs the body’s ability to clear the HPV infection. This is relevant for people living with Human Immunodeficiency Virus (HIV) and those who have received organ transplants requiring immunosuppressive medications. For people with HIV, consistently taking antiretroviral therapy (ART) to maintain a higher CD4 cell count and suppress the viral load is an important step in managing this risk. Managing the underlying immune condition helps the body fight off the persistent HPV infection.
Strategies for Early Detection
Early detection focuses on identifying and treating precancerous lesions, known as high-grade squamous intraepithelial lesions (HSIL) or anal dysplasia, before they can progress to invasive cancer. Screening is not recommended for the general population because anal cancer is rare, but it is strongly recommended for high-risk groups whose incidence rates can be 10 to 70 times higher than the general public. These high-risk individuals include men who have sex with men (MSM), people living with HIV, and those with a history of other HPV-related cancers like cervical or vulvar cancer.
Screening for high-risk individuals often involves an anal Pap test (anal cytology) or HPV testing, which collects cells from the anal canal to check for abnormal changes. If the initial screening test is abnormal, the next step is typically a high-resolution anoscopy (HRA). HRA uses a magnified camera to visually inspect the anal lining and allow for a targeted biopsy of any suspicious lesions. The digital anorectal exam (DARE) is an additional component of screening, where a healthcare provider manually feels for any lumps, masses, or other abnormalities in the anal canal.
It is important to be aware of symptoms that could indicate anal cancer, as early-stage disease is highly treatable. Symptoms can include unexplained rectal bleeding, a lump or mass near the anus, persistent pain or a feeling of fullness in the anal area, or a change in bowel habits. Because these symptoms can also be caused by more common, less serious conditions like hemorrhoids, any persistent or concerning change should be promptly evaluated by a healthcare professional.