Is AIN cancer?
No. AIN (Anal Intraepithelial Neoplasia) is a condition that can develop into cancer in some people. We don't know how often AIN develops into cancer, but we do know that it's a minority. We distinguish between high-grade and low-grade AIN. As far as we know, only high-grade AIN (HGAIN) is a precursor to anal cancer. Two large studies are currently underway in England and the United States to map the natural course of HGAIN (and thus the risk of developing anal cancer).
How does AIN develop? AIN is caused by certain types of the human papillomavirus, HPV. HPV is a virus with more than 100 strains, some of which are sexually transmitted. Although most HPV types are harmless, some types, primarily HPV 16 and 18, can cause cancer.
HPV can infect the lower layers of the mucosa through small (undetectable) injuries to the anal mucosa. The virus penetrates mucosal cells and causes the virus to multiply. This situation can persist for years, and most people are able to clear the abnormalities over time. However, in some people, the function of the mucosal cells can become so disrupted that cancer eventually develops.
I've had good CD4 counts for years, am I also at increased risk for AIN? Yes, unfortunately. Even people who have been receiving adequate treatment for years and have high CD4 counts are at increased risk for AIN and anal cancer. However, the lower your CD4 count has ever been, the higher this risk.
What is the difference between high-grade and low-grade AIN? Low-grade AIN (LGAIN) is generally considered a harmless abnormality. However, we often see low-grade and high-grade AIN coexist, and someone with LGAIN is therefore considered "at risk" and should be monitored.
High-grade AIN (HGAIN) is considered a precursor to anal cancer. However, the risk of developing anal cancer if you have HGAIN is unknown.
What is the risk of developing cancer if you have (high-grade) AIN?
The answer is unknown. Some studies show a risk of around 15% within a few years. Other studies show a much lower risk, between 3-4% over 10 years. For comparable cervical abnormalities in women, this risk is 30% over 30 years. The fact is, we don't yet know the exact course of HGAIN. Currently, two large studies are underway in England and the United States that are mapping the natural course of HGAIN (and thus the risk of developing anal cancer).
Can you also contract HPV without having anal sex?
HPV is highly contagious, and almost everyone who is sexually active will come into contact with multiple HPV types during their lifetime. Anal sex is the main risk factor for contracting anal HPV. However, it can also be easily transmitted through toys, fingers, and even towels. In women, the distance between the vaginal opening and the anus is very short, and HPV can easily be transferred to the anus, for example, when using toilet paper.
How can you prevent HPV infection? A condom offers some protection, but as mentioned above: HPV is highly contagious, and almost everyone who is sexually active (MSM (men who have sex with men) or heterosexual) will come into contact with one or more HPV types during their lifetime. The more frequent (unsafe) contact, the more likely it is that someone will become (re)infected with an HPV type.
Is my partner at increased risk for AIN/HPV? Yes and no. The cause of AIN, HPV, is highly contagious. In a steady relationship, you can assume you've been infected with each other's HPV types for a long time. Some people are better at clearing HPV than others. With changing partners, new HPV infections can naturally occur, which can be transmitted to a potential steady partner. In this sense, you can infect your partner with HPV types that could pose a risk in the long term.
How many HIV+ homosexual men have HPV? More than 90% of HIV+ homosexual men have one or more HPV types in their anus, usually oncogenic (high-risk) HPV. By comparison, 64% of HIV-negative homosexual men carry HPV (over half have oncogenic HPV).
How many HIV+ homosexual men have AIN? Between 50 and 80%. Of these, half have high-grade AIN (HGAIN). These percentages are much lower in HIV-negative men.
Why is screening for AIN being performed? In the Netherlands, there is no actual screening for AIN yet. However, we are trying to map the problem as much as possible through research. Given the high prevalence of anal cancer among HIV+ homosexual men, the link between AIN and anal cancer, and the similarities with cervical cancer (for which a highly effective screening program has existed since the 1960s), we believe that screening for and treatment of AIN can prevent anal cancer.
Are there plans for national screening for AIN? Although there is a lively discussion, a national screening program has not yet been implemented. This will depend on several important studies in the coming years on the risk of progression of AIN to anal cancer, and the role of AIN screening and treatment in preventing this.
I am being/have been screened for colon cancer in the new population screening program. Will anal cancer/AIN also be screened? No. Anal cancer is a different disease than colon cancer and unfortunately cannot be detected with the colon cancer screening program. Colonoscopy unfortunately doesn't allow for a good visualization of the anus, and AIN is usually missed.
How successful is treatment for HGAIN, and how often does HGAIN recur after successful treatment?
In the Netherlands, HGAIN is usually treated with electrocoagulation (burning). The success rate is 50%. Other treatment options have a lower success rate (such as treatment with imiquimod or 5-fluorouracil creams) or have not yet been (sufficiently) studied (such as nitrogen, laser, etc.). For AIN on the external anus, imiquimod is the first-choice treatment.
After successful treatment of HGAIN (meaning the lesions have disappeared), around 60-70% develop HGAIN again within a year and a half after treatment.
Extensive research is being conducted to improve these success rates.
How long does the treatment take? How often do I need to return?
The treatment consists of electrocoagulation (burning), performed in one or two sessions with a 12-week interval.
What are the side effects/risks of the treatment?
The most common side effects are local irritation/burning and blood in the stool. This lasts a few days at most. Rare complications may include infection, perforation (a hole in the bowel), or severe bleeding. This almost never occurs, and we haven't seen it since we started screening for AIN in 2007.
Can I choose not to have it treated?
Yes. You decide whether to accept a treatment recommendation. Based on what we currently know about AIN and anal cancer, we recommend treatment for HGAIN.
What is the policy elsewhere in the world? What is your view on the Australian position?
In San Francisco and New York, all HGAIN is treated, while in Sydney, a wait-and-see approach is often chosen, with patients closely monitored. In Amsterdam, we fall somewhere in between. The Australian group has shown that HGAIN can disappear spontaneously. However, in the same studies, anal cancer has also developed in a number of people. As long as we can't distinguish between HGAIN that does and doesn't develop into anal cancer, we believe it's important to treat all HGAIN and not take unnecessary risks.
Is it worthwhile to get vaccinated against HPV?
This is not yet known, although there are indications that HPV vaccination in HIV+ people may be beneficial. A large study is currently underway at the AMC, Onze Lieve Vrouwe Gasthuis, and the DC Klinieken Oud Zuid (Old South Medical Center) on HPV vaccination in HIV-positive men treated for high-grade AIN. These results will be available within a few years.
In addition, there is a public debate about the merits of vaccinating boys. The current HPV vaccines (Cervarix, Gardasil) are most effective at a young age, before exposure to different HPV types. HPV vaccination for 12-year-old girls has been included in the national vaccination program to prevent cervical cancer. Meanwhile, studies have also shown that HPV vaccination protects against AIN in young homosexual men. Therefore, it is also beneficial to vaccinate boys at a young age. |
