Anal cancer and HIV

Mareike Günsche |

Key points

  • Rates of anal cancer are higher in people with HIV than other people.
  • Most people who have abnormal cell changes in their anus do not go on to have anal cancer.
  • However, treating these abnormal cell changes reduces the risk of getting anal cancer later on.
  • Many guidelines now recommend screening for anal cancer in people who don’t have symptoms, but in reality this is not yet widely available.
  • Younger people with HIV should get the HPV vaccine to prevent anal and other cancers.

Anal cancer is a disease in which cancer cells are present just inside or immediately outside the anus.

Most cases of anal cancer are linked to human papillomavirus (HPV), a very common infection that can be passed on during sex. HPV is not a single virus – there are about 150 types of HPV that have different effects. Some types of HPV don’t seem to do any harm, other types can cause anal and genital warts, while others can cause anal and cervical cancer. HPV16 and HPV18 are the types most likely to cause cancer.

Most adults have had HPV infection. Very often, the body can get rid of the virus without you ever knowing you had it. When you have HIV, your body might find it more difficult to get rid of HPV on its own.

A small number of people who have HPV develop abnormal cell changes in or around the anus. This is not cancer. And most people who have these abnormal cells do not go on to have cancer. It is important to distinguish between:

  • Infection with HPV.
  • Abnormal cell changes that don’t seem to be linked to cancer. They don’t need treatment. Doctors may refer to these abnormal cells as low-grade anal intraepithelial neoplasia (AIN) or low-grade squamous intraepithelial lesion (SIL). In this page, we call them low-grade AIN.
  • Abnormal cell changes that are associated with a small risk of developing cancer in the future. Often these abnormal cells will go away on their own, but in case they don’t, treatment is recommended. These abnormal cells may be called high-grade anal intraepithelial neoplasia (AIN) or high-grade squamous intraepithelial lesion (SIL). In this page, we call them high-grade AIN.
  • Anal cancer. Cancer cells grow and multiply out of control. They may form a mass (tumour) and invade nearby tissues. Anal cancer can be life threatening.

Preventing HPV and anal cancer

You can reduce your risk of HPV and cancer by getting vaccinated. HPV vaccination can prevent several cancers (including anal and cervical cancer) and also genital and anal warts.

The younger you are, the more likely you are to benefit. If you are older, it is more likely that you have already been exposed to several types of HPV, making the vaccine less effective.

The British HIV Association recommends that the following groups of people living with HIV receive the HPV vaccine:

  • women up to the age of 40
  • gay men and other men who have sex with men up to the age of 40
  • heterosexual men up to the age of 26.

Vaccination involves taking a course of three injections, over a six-month period. While younger people who do not have HIV may be given one dose, three doses are recommended for people with HIV. You can ask your HIV or sexual health doctor about getting vaccinated.

Using a condom during sex can also help to prevent HPV infection.

Who is at risk?

High-grade AIN and anal cancer are rare in the general population, but rates are much higher in people with HIV and other individuals with weakened immune systems.

People who have had anal sex as the receptive partner (‘bottom’), more sexual partners or genital warts are more likely to be infected with multiple types of HPV. This makes high-grade AIN and anal cancer more likely.

Nonetheless, high-grade AIN and anal cancer can develop in people who have never had anal sex or HIV.

Smoking makes abnormal cell changes happen more quickly. Stopping smoking can reduce your risk of anal cancer and may help prevent high-grade AIN progressing to cancer.

The risk of high-grade AIN and anal cancer increases as you get older.

Women who have previously had abnormal cervical screening results have a higher risk of anal cancer than other women. This is because HPV can spread between the genitals and the anus.

Anal cancer in people living with HIV

People living with HIV are at much greater risk of having high-grade AIN or anal cancer than people without HIV. It seems that HIV’s effect on the immune system reduces the body’s ability to keep HPV infection under control.

Gay and bisexual men living with HIV have the highest risk of developing anal cancer. However, women and heterosexual men with HIV also have a higher risk of anal cancer compared to people without HIV. That’s why screening and preventing anal cancer is important for all people living with HIV.

aidsmap's Susan Cole talks about cancer and HIV.

Taking effective HIV treatment significantly lowers your risk of developing cancer. A higher CD4 count and CD4/CD8 ratio are both linked to lower risks of cancer in people with HIV. Nonetheless, anal cancer can occur in people taking effective HIV treatment. Because people with HIV are living longer, cancers like this have more time to develop. 

If you are diagnosed with anal cancer but haven’t been tested for HIV, your doctor will discuss HIV testing with you. This is because people who have anal cancer sometimes have HIV without realising it.


Anal cancer can cause symptoms in the anal area, including bleeding, pain, discomfort, itching, small lumps or ulcers on or inside the anus, a discharge, and difficulty controlling your bowels.

Sometimes, anal cancer doesn’t cause any symptoms at all. And sometimes symptoms can be similar to other common, less serious health problems, like piles (haemorrhoids) and anal fissures.

People with low or high-grade AIN often have no symptoms, but sometimes it causes similar symptoms to anal cancer.

If you have any symptoms, it’s worth having them checked by a sexual health doctor or your GP. While some people are embarrassed or uncomfortable discussing this area of their body, it’s not unusual for doctors to examine the anus.

Diagnosis and monitoring

A clinical trial in the United States has found that screening and early treatment of high-grade AIN reduces the rate of anal cancer in people living with HIV by more than half (57%):

  • When receiving treatment for high-grade AIN, less than 2 in 1000 people developed anal cancer within 5 years.
  • When receiving only active monitoring for their high-grade AIN, about 4 in 1000 people developed anal cancer within 5 years.

These results support the inclusion of screening and early treatment of high-grade AIN in routine care for people living with HIV. Treating high-grade AIN could help prevent cases of anal cancer that would be much harder to treat later on. However, resources, like screening equipment and trained staff, are often limited and many people currently don’t have access to screening. More clinicians need to be trained to perform a procedure called anoscopy to make screening more widely available.

When you go to a screening appointment or if you have an appointment because you’re experiencing any symptoms, a first check could be a rectal examination. This involves your doctor inserting a gloved finger into your back passage to feel for any lumps or swellings. This is usually quick and painless.



A collection of related diseases that can start almost anywhere in the body. In all types of cancer, some of the body’s cells divide without stopping (contrary to their normal replication process), become abnormal and spread into surrounding tissues. Many cancers form solid tumours (masses of tissue), whereas blood cancers such as leukaemia do not. Cancerous tumours are malignant, which means they can spread into, or invade, nearby tissues. In some individuals, cancer cells may spread to other parts of the body (a process known as metastasis).

anal intraepithelial neoplasia (AIN)

An abnormal growth on the surface of the rectum or anal canal which, when observed with a microscope, suggests that the cells could be malignant (cancerous).

human papilloma virus (HPV)

Some strains of this virus cause warts, including genital and anal warts. Other strains are responsible for cervical cancer, anal cancer and some cancers of the penis, vagina, vulva, urethra, tongue and tonsils.


Any perceptible, subjective change in the body or its functions that signals the presence of a disease or condition, as reported by the patient.



A medical treatment using radiation (also known as radiation therapy). Beams of radiation may be produced by a machine and directed at a diseased area from a distance. Alternatively, radioactive material, in the form of needles, wires or pellets may be implanted in the body. Many forms of cancer can be destroyed by radiotherapy.

You can also do a self-exam to check for anal lumps. This is called a Digital Ano-Rectal Examination (DARE). This can help you detect lumps when they’re smaller and easier to treat. You can find more information on how to do this exam on yourself or your partner on the Body Positive New Zealand website.

Your doctor may also recommend an anal swab (also called anal smear test). For this, your doctor will pass a small swab just inside your anus to collect cells, which are suspended in fluid, stained and examined under a microscope (a process called cytology). This is usually quick and painless. The swab can also be used for an HPV test to check to see if you have a type of HPV that increases your risk for anal cancer. This is not enough to diagnose AIN or anal cancer but can be used as a first check. Or it can be used to check for AIN.

A different technique to check for AIN is anoscopy. Its results seem to be more accurate in people living with HIV than the smear test. A small magnifying device is inserted into the anus in order to visually examine the cells of the anal canal. This should take a few minutes and is not painful.

If necessary, a biopsy will be taken during the anoscopy. Tiny samples of tissue are removed under local anaesthetic, which numbs a small part of the body, to minimise any discomfort. These cells will then be examined under the microscope to check if they are normal cells, abnormal cells or cancerous cells. This is called a histology.

Other examinations can include proctoscopy, which is similar to anoscopy but can also examine the rectum. Again, biopsies may be taken of what seems to be abnormal tissue. This is necessary to check if cells are cancerous.

If you have anal cancer, you will need further scans to find out more about the position of the cancer and to see if it has begun to spread. These include a CT (computerised tomography) scan and an MRI (magnetic resonance imaging) scan.

Treatment and management

If you have low-grade AIN, no treatment is needed. You may be asked to come back in six or twelve months for another screen.

If you have high-grade AIN, one of the following treatments may be offered:

  • Surgery to remove lesions that cover only a small area.
  • A cream that you apply yourself to the affected area, such as imiquimod (Aldara) or 5-flourouracil (Efudix). You’ll do this two or three times a week for three or four months. This works best for wide areas of AIN, especially in the external skin.
  • Ablative therapies. Various techniques are used to destroy the affected areas with heat or by freezing them. Some of the names of these techniques are electrocautery, laser ablation, infrared coagulation and cryotherapy.

You may experience some side effects when you receive treatment for AIN, for example skin irritation, pain and bleeding.

None of these treatments has a 100% success rate – in many cases, the problem recurs. This may be because the treatments do not get rid of the underlying HPV infection.

If you have anal cancer, the recommended treatment is chemoradiotherapy. This is a combination of chemotherapy and radiotherapy, usually over a period of five weeks. Chemotherapy uses strong drugs to destroy cancer cells and prevent the cancer from spreading. Radiotherapy uses beams of radiation to destroy the cancer cells, in a localised area only.

Chemoradiotherapy is usually successful but does sometimes cause long-term complications. These can include problems in relation to your bladder, bowels and sexual function.

If chemoradiotherapy doesn’t get rid of all the cancer or if there are signs that it has come back, surgery may sometimes be used.

The same types of treatment are used for people with HIV and people without HIV. The treatment you are offered shouldn’t be different to that of other people just because you have HIV.

It’s recommend you continue to take HIV treatment during your cancer treatment, or if you haven’t already, that you start. Taking HIV treatment during cancer treatment is associated with living longer and a lower risk of opportunistic infections. Chemotherapy and radiotherapy both suppress the immune system, which may result in a significant drop in your CD4 count. You should be given drugs to prevent opportunistic infections (this is known as prophylaxis). Your CD4 count may be checked more often after cancer treatment than it would be normally.

There can be drug-drug interactions between cancer treatments and HIV treatments. For this reason, it may be necessary to make some adjustments to your HIV treatment or your cancer treatment.

As treatments for HIV and cancer can both cause side effects, your doctors should keep an eye on how they are affecting you. In some cases (such as nausea from chemotherapy), highly effective treatments to limit side effects are now available. If side effects become too severe, your doctors may need to adjust one of the treatments. We recommend you speak to your doctor if you’re worried about side effects of your treatment.

You need to see specialist doctors for the monitoring and treatment of both AIN and anal cancer. Depending on where you are, your local hospital may not have the necessary experience in this area. It's very important that the doctors treating your cancer and your HIV work together. There should also be contact between the pharmacists in the cancer and HIV clinics. 

A multi-disciplinary team will make recommendations about your treatment. This team may include an oncologist (a doctor who specialises in treating cancer), a radiologist (a doctor who interprets the results of scans or provides radiotherapy) and a pathologist (a doctor who examines tissue for cancer cells). You will be supported by a cancer specialist nurse during your cancer journey. If a cure is not possible, palliative care can relieve pain and other symptoms and help you maintain the best possible quality of life.

Information and support

For more information, you may find the website of Macmillan Cancer Support helpful: In the UK, you can also contact their helpline team on 0808 808 0000.

For more information on cancer organisations around the world, you may find helpful links on the International Cancer Information Service Group website or on the American Cancer Society website.

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