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Anal cancer is cancer that starts in the anus, which is the last part of the digestive tract where stool leaves your body. Anal cancer occurs when certain cells in the anus or the anal canal (what connects the anus to the rectum) start to grow and divide abnormally and uncontrollably, causing a tumor that can block the canal or spread to nearby tissues and organs.

Anal cancer can cause symptoms similar to hemorrhoids, such as bleeding from the rectum or lumps in the anus. If you experience changes like this, a healthcare provider can determine whether anal cancer is the cause. While most anal cancers are not aggressive, early detection is key because survival rates are better the earlier the stage at diagnosis.

Anal cancer is not common. The lifetime diagnosis risk is about 1 in 500. Older adults are more likely to develop it, with the average age of diagnosis being in the early 60s.

Types of Anal Cancer

Anal cancer has different types depending on where in the anus the cancer started. The types of anal cancer include:

• Squamous cell carcinoma: About nine out of 10 cases of anal cancer in the United States are squamous cell carcinomas, making it the most common type of anal cancer. The cancer starts in the squamous cells that line most parts of the anal canal and grow beyond the surface into the deeper tissues.
• Adenocarcinoma: This is a rare type. It starts in cells of the anal gland that are under the moist lining membrane of the anal canal or in cells in the upper part of the anus, closer to the rectum. They are often detected when the cancer has advanced.
• Melanoma (anal skin cancer): Melanoma is a type of anal cancer that starts in melanocytes, which are cells in the skin around the anus that make the melanin pigment that gives skin its color.
• Basal cell carcinoma: Similar to melanoma, basal cell carcinoma develops in the perianal skin and is usually treated with surgery. This type is more common in other parts of the body, particularly areas exposed to the sun, like the hands and face.
  

Anal Cancer Symptoms

Anal cancer symptoms can include:

• Bleeding from the anus or rectum
• Discharge or drainage (of pus or mucus) from the anus
• A lump in the anus
• Pain or pressure around the anus
• Anal itching
• A change in your bowel habits
• Swollen lymph nodes in your anal area or groin

Because the symptoms occur in the last part of the digestive tract that healthcare providers can easily reach and examine, the cancer is often detected early.

However, anal cancer does not cause symptoms for everyone—about 20% of people don’t experience symptoms. This particularly applies to the early stage, when the cancer hasn’t grown or spread.

What Causes Anal Cancer?

All cancers, including anal cancer, occur as a result of cell mutations. These are changes in genes and DNA that control how cells grow and function. The exact cause of the mutation in the anal cells is unknown.

Risk Factors

While it's unknown why some people experience cell mutations in the anus, researchers have identified some factors that appear to increase risk.

Anal cancer is more common in white women and Black men. It also occurs more in people who are over 50 years old.

Other risk factors include:

• Having HPV infection: About 91% of anal cancers per year in the U.S. are linked to an infection with the human papillomavirus (HPV), a common sexually transmitted infection (STI). There are over 150 types of HPV, but HPV-16 most commonly causes anal cancer, particularly squamous cell carcinomas. HPV makes proteins that can shut down tumor suppressor genes that normally work to keep cells from growing out of control.
• Having multiple sexual partners: People who have many sexual partners are at a higher risk for developing anal cancer. This could be because they have a higher tendency to contract STIs like HPV and HIV (which is also a risk factor). People on the receiving end of anal sex may also be at higher risk.
• Having a weakened immune system: When your immune system is low, it’s unable to fight off infections effectively. Viral infections like HPV and HIV can become more active, contributing to cancer. Certain medications and treatments, like organ transplants, can also lower your immunity, increasing your anal cancer risk.
• Smoking: This habit is commonly linked to lung cancer, but the carcinogenic (cancer-causing) chemicals in tobacco can also travel to other parts of the body.
• Having anal warts and certain other cancers: People who have had genital warts or cancer of the vagina, cervix, or vulva are at a higher risk for developing anal cancer. This may be because anal warts and these cancers are linked to HPV infection.

Diagnosis

After a physical examination and a review of your personal and family health history, your healthcare provider may perform or order the following tests to make a diagnosis:

• Digital rectal examination: The provider examines your anus and rectum by inserting a lubricated, gloved finger into the anal canal to feel for any abnormalities.
• Anoscopy: Your healthcare provider will gently push a short hollow tube with a light on its end into your anus to view the anus and lower end of the rectum.
• Prostoscopy: Similar to anoscopy, protoscopy uses a thin, tube-like instrument with a light and a lens at its end to look inside the anus and rectum for abnormal areas. The tube can also come with a tool for removing tissue samples that will be checked in the lab for cancer.
• Imaging tests: This includes tests like endorectal ultrasound that uses sound waves, a computed tomography (CT) scan that uses X-rays, and magnetic resonance imaging (MRI) that uses radio waves to generate images of the rectum and anal canal. They can be used to find cancer and also check how far cancer has spread.
• Biopsy: If your imaging tests or other examinations suggest you could have anal cancer, your healthcare provider may need to take a tissue sample (biopsy) from the abnormal area. The sample will be sent to the laboratory to test whether cancer cells are present. A biopsy is the definitive test for cancer.
  

Treatments

The goal of anal cancer treatment is to get rid of all the cancer cells. Different treatment options are available and may depend on how advanced the cancer is, where the tumor is, and whether it responded well to or came back after initial treatment.

Chemoradiation

Usually, anal cancer is treated with a combination of radiation therapy and chemotherapy.

Radiation therapy uses high-energy beams to target and kill cancer cells. A machine outside the body usually sends radiation to the anus. Sometimes, a tube of radioactive substances is put directly into the anus.

Chemotherapy can kill cancer cells or stop them from growing. It can be taken by pill or through a vein and is put right into the blood to be spread through the body.

Surgery

For smaller tumors, surgery alone is typically used instead of radiation and chemotherapy.

Your healthcare provider may recommend different types of surgery depending on the size and location of the tumor. For example:

• Resection: This removes a small tumor in the anus that has not spread. Some healthy tissue around the tumor will also be removed to ensure all cancer cells are gone.
• Abdominoperineal resection: This removes the anus, rectum, and a small part of the bowel. The surgeon then constructs a colostomy, an opening in the lower belly so waste can be diverted from the body and collected into a pouch. This treatment may only be used when other treatment options don’t work.
  

Immunotherapy

Immunotherapy aims to boost your immune system to help it fight the anal cancer cells. This form of treatment is often given through a vein. The medication contains substances made from living organisms.

How often and how long you receive it depends on factors like how advanced your cancer is and how your body reacts to the treatment.

Clinical Trial Treatments

Researchers constantly conduct studies to test new drugs and treatments. One such treatment being studied in clinical trials is radiosensitizers, which are medications that make tumor cells more sensitive to radiotherapy.

You can ask your healthcare provider about whether there is a clinical trial on anal cancer treatment that you can sign up for and whether they recommend you enroll. If you do take part, you can drop out at any point.

How To Prevent Anal Cancer

Since the exact cause of anal cancer is unknown, there is no known way to prevent it entirely. However, doing the following may significantly reduce your risk:

• Go for regular check-ups, especially if you have had an HPV or HIV infection
• Avoid smoking
• Speak to your healthcare provider about receiving an HPV vaccine
• Take your HIV medications—if you have HIV—to keep the infection at undetectable levels
• Use condoms during sex
  

Complications

Anal cancer and its treatment can cause complications such as:

• Reduced sex drive
• Bleeding from the rectum
• Bowel dysfunction
• Inflammation of the rectum's lining
• Radiation side effects like painful bowel movements, vaginal irritation, and skin changes in the area where the radiation was given
• Adverse effects of chemotherapy, including hair loss and nausea
• Wound infections, scarring, strictures (bowel blockage), and fistulas (abnormal connections between the anus and other organs) after surgery
  

Living With Anal Cancer

Being diagnosed with anal cancer can cause you to feel afraid, stressed, and anxious. The diagnosis is often difficult to deal with, but there is much hope.

If the cancer stays where it was found, there is about an 83% chance someone will live for at least five years. If the cancer has spread to nearby areas, the five-year survival rate is about 67%. The chances of living longer and even achieving remission increase more with the right treatment—and indeed, treatments are now available to target different aspects of cancer growth.

Rely on your healthcare team to give you the best treatment, and consider that learning more about your condition may help you actively participate in your treatment plan. Also, lean on any family or friends you may have for support; they may be able to help you overcome your low moments. Be open to accepting physical and emotional support while practicing self-care and advocating for your health.

Frequently Asked Questions

• Is anal cancer curable?

  Anal cancers have a high cure rate, especially if diagnosed and treated in the early stages. Combining chemotherapy and radiation therapy is considered the gold standard treatment for most anal cancers.

• Can a colonoscopy detect anal cancer?

  A colonoscopy is not specifically for diagnosing anal cancer; it’s for screening the colon and rectum for any abnormalities. If an abnormality found during a colonoscopy suggests anal cancer, the provider will likely take a sample to test for cancer cells.

• What's the difference in symptoms between hemorrhoids and anal cancer?

  Bleeding caused by anal cancer is often persistent and accompanied by other symptoms like fatigue, weight loss, and pain. Hemorrhoid-related bleedings are often intermittent and more pronounced during bowel movement. Hemorrhoids also cause the inability to control bowel movement and a sensation that the bowels are not emptying.

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