Anal cancer occurs in the anus, which is at the end of the gastrointestinal tract. It is different from and less common than colorectal cancer, which is cancer of the colon or rectum.

Anal cancer is rare, but the number of new cases is rising.

According to the American Cancer Society (ACS), there are likely to be about 8,300 new cases in 2019. Of these, 5,530 will affect females, and 2,770 will affect males. The ACS expect around 1,280 people to die from anal cancer, including 760 females and 520 males.

Various factors may increase the risk of anal cancer, but infection with two types of human papillomavirus (HPV) appears to underlie 91% of cases.

Anal cancer is rare before 35 years of age. The average age of diagnosis is when a person is in their early 60s. Around 1 in 500 people will develop anal cancer at some time.

At first, anal cancer may resemble hemorrhoids. Anyone who notices changes in the anal area should see a doctor. Often, they do not have cancer. If they do, an early diagnosis is more likely to lead to a positive outcome.

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Anal cancer is more common in woman than in men.

Common symptoms of anal cancer include:

  • bleeding from the rectum
  • itching around the rectum
  • pain or a feeling of fullness around the anus
  • lumps that may resemble hemorrhoids
  • changes in bowel movements
  • narrow stools
  • a discharge from the anus
  • swollen lymph nodes in the groin or anal area

Some of these symptoms can also be the result of hemorrhoids, anal warts, or anal tearing. However, a person should see a doctor if these changes occur, to rule out cancer.

Anal cancer develops when cells grow uncontrollably and form a tumor. Two types of cancer can form in the anus, depending on where the cancer starts.

Squamous cell cancer: The anal canal connects the rectum to the outside of the body. Squamous cells line the canal. These flat cells look like fish scales under the microscope. Most anal cancers are squamous cell carcinomas because they develop from squamous cells.

Adenocarcinoma: The point where the anal canal meets the rectum is called the transitional zone. It has squamous cells and glandular cells. Glandular cells produce mucus, which helps the stool pass through the anus smoothly. Adenocarcinoma can also develop from the glandular cells in the anus. Around 3–9% of anal cancers are of this type.

Risk factors

The risk factors for anal cancer include:

HPV: There is growing evidence that some types of HPV increase the risk of various cancers. Researchers have linked the presence of HPV16 to various cancers, including cervical cancer and some head and neck cancers.

Other cancers: People who have had another HPV-linked cancer seem to have a higher risk of anal cancer. For females, these include vaginal or cervical cancer, or a history of precancerous cells in the cervix. Males who have had penile cancer have a higher risk, also.

HIV: People with HIV have a higher risk of developing anal cancer than people without the virus.

Reduced immunity: People with a suppressed immune system have a higher risk. The immune system can be weaker in people with AIDS and those who take medications following a transplant.

How can people with a weak immune system stay healthy? Find out here.

Sexual activity: Having multiple sex partners can increase the risk, as this increases the chance of exposure to HPV.

Sex: Anal cancer is more common in females than in males. However, among African Americans, it is more common among males up to the age of 60 years, after which it is more likely to affect females.

Age: As people get older, their chances of developing anal cancer increase.

Smoking: Smokers have a significantly higher risk of several cancers, including anal cancer. Quitting may lower the risk.

Treatment for anal cancer will be different for each person.

Factors that affect the options for treatment include:

  • the size of the tumor
  • the cancer grade, as high grade cancers can be more aggressive
  • whether cancer has spread
  • the individual's age and overall health

Surgery, chemotherapy, and radiation therapy are the main treatment options.

Surgery

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Surgery is one possible treatment for anal cancer.

The type of surgery depends on the size and position of the tumor.

Resection: The surgeon removes a small tumor and some surrounding tissue. This is only possible if cancer has not affected the anal sphincter, or muscle. After this procedure, the person will still be able to have a bowel movement.

Abdominoperineal resection: The surgeon removes the anus, rectum, and a section of the bowel. The person will not be able to have a bowel movement, and so the surgeon will construct a colostomy. In a colostomy, a surgeon brings the end of the bowel to the outside of the abdomen. A bag then covers the stoma, or opening, and collects the stools outside the body.

A person with a new colostomy may feel anxious, but they can lead a normal life, play sports, and be sexually active. However, a doctor will try to avoid surgery that changes physical structures, as far as possible.

Chemotherapy and radiotherapy

A doctor may recommend chemotherapy, radiation therapy, or both. People may have these treatments at the same time or one after the other. If these approaches work, the person may not need a colostomy.

Chemotherapy uses drugs that kill cancer cells or prevent them from dividing. The doctor may give them orally or by injection.

Radiation therapy uses high energy rays that destroy cancer cells. In external radiation, a machine produces a beam that targets the malignant cells. Internal radiation involves inserting radioactive material into the body, from where it emits ongoing radiation.

Both radiation therapy and chemotherapy can have adverse effects. Radiation therapy can lead to soreness and blistering around the anus. A doctor may prescribe therapies to reduce the severity of side effects.

Other short term effects of combining radiation and chemotherapy for anal cancer can include other skin problems and gastrointestinal issues.

Long term effects may include:

  • sexual dysfunction
  • a higher risk of blood clots in the legs
  • narrowing of the anus
  • bladder problems
  • inflammation of the lining of the rectum

A doctor will work with the individual to choose the best option for them.

Immunotherapy

Scientists have been looking into an emerging treatment they call immunotherapy.

Specific drugs can boost the immune system's defense from some types of cancer.

Researchers hope that immunotherapy might one day be an option for anal cancer as well.

The outlook for a person with anal cancer will depend to some extent on the stage at which they receive a diagnosis. Experts use statistics to work out how many people can expect to live another 5 years or more after a cancer diagnosis.

According to the ACS, the chances of living at least 5 years with anal cancer are:

  • 82% for localized cancer, which has not spread beyond the original site.
  • 64% for regional cancer, which has only spread to nearby tissues.
  • 30% for distant cancer, which affects other areas or organs, for example, the liver.

Specialists have based these predictions on disease figures for 2008–2014. As medical knowledge and treatments improve, so should the outlook.

Other factors affecting the outlook include the individual's overall health and age. However, anyone who receives a cancer diagnosis at an early stage will have a better chance of effective treatment than those whose diagnosis is later. For this reason, it is essential to see a doctor soon if changes occur in or around the anus.

It is often possible to detect anal cancer in the early stages, especially if it occurs in the lower part of the anal canal.

To diagnose anal cancer, a doctor will:

  • ask the person about their symptoms
  • take a medical history
  • carry out a physical examination

If the doctor believes anal cancer may be present, they will refer the person to a colorectal surgeon, a doctor who specializes in bowel conditions.

The specialist may carry out a number of tests.

A rectal examination

The doctor may insert a proctoscope, anoscope, or sigmoidoscope into the anus to examine the area in more detail. This will help determine if the person needs a biopsy.

A biopsy

The doctor will take a small sample of tissue from the anal area and send it to the lab for examination under a microscope.

If the biopsy reveals cancerous tissue, the person will need further tests to find out how large the cancer is and whether it has spread.

A CT, MRI, or ultrasound scan can help confirm the results. This may include a rectal ultrasound, where the doctor inserts an instrument into the anus to be able to see the tissues more clearly.

What is a biopsy, and what does it involve? Learn more here.

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Using condoms when having sex may help prevent anal cancer.

To reduce the risk of anal cancer, a person can:

  • have the HPV vaccination before they become sexually active
  • use condoms when having sex
  • avoid or quit smoking

People should seek medical advice for any changes that affect the anus, even if these give no suggestion of cancer.

An individual can also ask a doctor about screening if they have a high risk, such as HPV infection.

Anal cancer is a relatively rare cancer with close links to the HPV. Having the HPV vaccination and seeing the doctor about any changes in the anal area can help reduce the risk of anal cancer and its complications. People with a higher risk should consider asking their doctor about screening.

Q:

Does having anal sex increase the risk of anal cancer?

A:

Yes. The risk of anal cancer increases with a greater number and exposure to multiple sexual partners, especially with anal contact. The most common risk factor for anal cancer is infection with the human papillomavirus (HPV). HPV is a sexually transmitted virus that people can transmit during anal sex

Christina Chun, MPH Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.