What is Anal Cancer?

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Anal cancer is a rare cancer that arises from the anus. The anus is comprised of the anal canal, a passage about 3-4 cm or 1.5 inches and the anal margin, also known as perianal skin, the opening where feces is excreted from the body. Anal cancer refers to several types of cancer that can develop in this area.

The most common symptoms of anal cancer include bleeding from the anus, itching around the anus, and anal pain.^[1] Many non-cancerous conditions have similar initial symptoms, such as anal fissure or hemorrhoids.

Anal cancer tends to spread slowly. With early treatment, in many cases, it has a relatively good prognosis.^[2]

This condition tends to affect older adults between the ages of 50 and 80, and is slightly more common in women than in men.^[3] About 1.8 per 100,000 people in the U.S. are newly diagnosed with anal cancer per year.^[4]

Treatment depends on the type of anal cancer and stage of diagnosis, but typically involves a combination of surgery and chemotherapy. Recovery rates tend to be better in cases where the cancer is diagnosed early.

Types of anal cancer

Anal cancers are often divided into two groups, which are sometimes treated differently:^[5][6]

• Cancers of the anal margin: These begin in the cells of the anal margin – the edge of the anus that can be partly seen as darker skin on the outside of the body. They are more common in men and have a relatively good prognosis.
• Cancers of the anal canal: These begin in the cells of the anal canal –the inner part of the anus, connecting the rectum – the final section of the intestine, that connects it to the anus – to the anal margin. They are more common in women and have a relatively worse prognosis.

There are several different types of anal cancer. These include:^[5][6]

Carcinoma in situ

Carcinoma in situ is considered by some doctors to be the earliest form of anal cancer, and by others to be a precancerous condition, which may develop into cancer.

In carcinoma in situ, there are abnormal cells on the surface layer of the anus, which have not spread to any deeper layers.

Squamous cell carcinomas

Squamous cell carcinomas are the most common type of anal cancer, making up 80 or 90 percent of cases. It starts in the squamous cells which form the surface layer of the lining the anal margin and anal canal. This is similar to carcinoma in situ, except that these cancers have grown into the deeper cells and layers of the anal canal, and may spread.

Adenocarcinomas

Adenocarcinomas make up about 15 percent of anal cancers. These may start in glands in the anal area or in the cells that line the part of the anus near the rectum.

Skin cancers

Some anal cancers are basal cell carcinomas or malignant melanomas – two different types of skin cancer. Only a very small portion of anal cancers are skin cancers.

Other types of anal cancer

Other, very rare types of anal cancer include:

• Lymphomas
• Gastrointestinal stromal tumors (GIST)

Anal cancer symptoms

Anal cancer may present with a wide range of symptoms, or may have no symptoms at all. The most common symptoms of anal cancer include:^[1][7]

• Bleeding from the anus
• Anal or pelvic pain
• Anal itching
• Discharge from the anus
• A lump in or near the anus

Less common symptoms may include:^[1][7]

• A change in bowel habits, such as increased gas, losing control of one’s bowel, or hard or soft feces
• Severe or complete constipation
• Swollen lymph nodes in the groin and anal region

Most often these symptoms are more likely to be caused by non-cancerous conditions, such as hemorrhoids, anal fissures, or anal warts. If any of these symptoms are present, it is important to see a doctor quickly so that the cause can be found and treated appropriately.

Anal cancer causes

The causes of anal cancer are not well understood. However, certain factors are thought to increase a person’s risk of developing the condition. It is most commonly linked to human papillomavirus (HPV), a sexually transmitted infection (STI) which more commonly causes genital and anal warts.

Anal cancer risk factors

Factors that may increase the risk of developing anal cancer include:^[3][8]

• Human papillomavirus (HPV)
• A history of cervical or vaginal cancer
• A lowered immune response, such as occurs with HIV or from medication taken after organ transplantation
• Smoking tobacco
• Being over 50
• Receptive anal intercourse
• Repeated inflammation in the anal region

Anal cancer is most common in people between the ages of 50 and 80, and it is slightly more common in women than in men.

Anal cancer diagnosis

Symptoms of anal cancer may be caused by a number of other conditions, including hemorrhoids, anal fissures, or anal warts. A doctor will need to rule these out in the diagnostic process.

Anal cancer tests

As the first step, a doctor will typically take the person’s medical history and perform a physical examination. In addition, a doctor may perform the following tests:^[2][9]

• Digital rectal examination (DRE), which involves inserting a gloved finger into the anus to feel for lumps or other abnormalities.
• Anoscopy may be performed if the doctor feels a suspicious area during DRE. The doctor will insert into the anus a thin, flexible tube with a light and camera on the end called an anoscope, allowing them to see the inside of the anus.
• Biopsy, a procedure to remove a small amount of tissue for examination under a microscope, can make a definite diagnosis. The type of biopsy will depend on the location of the abnormal cells, but may include an excisional biopsy to remove an entire lump.
• Ultrasound, X-ray, computed tomography (CT scan), magnetic resonance imaging (MRI) or positron emission tomography (PET scan) may be used to investigate the size of the cancer.

If any of the results of these tests are positive for cancer, further investigation is done to confirm the staging of the cancer.

Anal cancer screening in people at high risk

Screening is a way of identifying apparently healthy people who may be at an increased risk of a particular condition. This is often done to help identify cancers at the earliest stages, when treatment can provide the best prognosis.

Anal cancer is not very common, so screening of the general public is not widely done. However, people who are considered to have a higher than average risk of developing anal cancer may be advised to undergo regular screening for the condition.

Screening tests for anal cancer may include:^[10]

• Digital rectal examinations
• Anal cytology testing, also known as an anal Pap test or smear

An anal Pap smear is very similar to a Pap smear for cervical cancer. The anal lining is swabbed to collect cells, which are then looked at under a microscope to see if any cells show pre-cancerous signs.

Those who might benefit from anal cancer screening include:^[10][11]

• People who are HIV positive
• Men who have sex with men
• Women who have had cervical cancer or vulvar cancer
• People who take immunosuppressants after receiving an organ transplant
• Occasionally, people with a history of anal warts are recommended to have screening

Anal cancer treatment

The treatment of anal cancer depends on the size of the cancer, the exact type of cancer and whether the cancer has spread. The treating doctor can give the best advice as to treatment.

Anal cancer can be treated by one or more of the following:

• Radiotherapy
• Surgery
• Chemotherapy

Often, the first step in treatment for anal cancer is a combination of radiotherapy and chemotherapy, known as combined modality therapy (CMT). Anal cancer may be curable in this way without the need for surgery.

Anal cancer chemotherapy

The general aims of chemotherapy treatment for anal cancer are to destroy any tumor tissue and increase the likelihood of recovery.

Chemotherapy can sometimes have unpleasant side effects, such as hair loss, nausea and vomiting, fatigue and pain. A doctor will be able to advise on how best to manage the side effects, should they occur.

Read more about Chemotherapy Side-Effects.

Anal cancer radiotherapy

Also known as radiation therapy, this uses X-rays to destroy cancer cells. Radiation for anal cancer can have unpleasant side-effects, such as diarrhea, skin irritation and nausea. A doctor will be able to advise on how best to manage the side-effects, should they occur.

Anal cancer surgery

Surgery is not normally the first treatment for anal cancer. If needed, the type of surgery will depend on the type and size of tumor. There are two main types of anal cancer surgery:^[12][13]

Local resection

This removes the tumor and a small area of normal tissue around it. A local resection is commonly used for tumors on the anal margin – the skin at the end of the canal that meets the anus opening – that are small and have not spread to other tissues or to lymph nodes.

Local resection normally allows the sphincters to be saved, so that a person may continue normal bowel movements after surgery.

Abdominoperineal resection for anal cancer

Abdominoperineal resection (APR) is an operation in which the anus and rectum are removed, possibly along with some nearby groin lymph nodes. APR requires a colostomy, in which the end of the colon is diverted out through the wall of the abdomen, leading to an external bag to collect stool and other human waste.

Good to know: APR is only used if other treatments don’t work or if the cancer returns after treatment. Nowadays, APR can almost always be avoided by using chemotherapy and radiotherapy instead.

APR surgery is more likely to cause long-term complications, such as urinary incontinence and sexual dysfunction. A doctor will be able to advise on how best to manage side-effects, should they occur.

Anal cancer prognosis

Anal cancer tends to spread slowly. With early treatment, in many cases it has a relatively good prognosis and may be curable.^[2]

In order to determine how the cancer should be treated, such as whether potentially life-changing surgery will be required, doctors will find out the size of the cancer and whether it has spread or metastasized to nearby lymph nodes or to distant organs, in a process known as staging.

Earlier stage cancers are more likely to be curable than more advanced stages, i.e. with larger tumors, and/or cancers that have spread.

Factors associated with poorer outcomes may include:^[14][15]

• Tumors in the anal canal rather than the anal margin
• Tumors greater than 5cm
• Tumors that invade nearby organs such as the urethra or bladder
• Lymph node involvement
• Being HIV positive

What are anal cancer survival rates?

Survival rates show what percentage of people live for a certain length of time after being diagnosed with cancer.

Survival rates are generally sorted into 5-year and 10-year time brackets. Because the statistic is based on people diagnosed over five years ago, the outlook may be better for those diagnosed today, since there are continuing improvements in treatment.

Survival rates include people who are free of disease or who experience few symptoms, as well as those who are still being treated for cancer, those who will survive for many more years and those who will not live much longer than the time bracket given.

Five-year survival rates for people with anal cancer in the U.S. are currently as follows:^[3][16]

• Localized anal cancer: About half of all anal cancers are found early, when they are localized, meaning they have not spread beyond the anus. The five-year survival rate is about 80 percent.
• Locally advanced anal cancer: If the cancer has spread to the lymph nodes or other areas around the anus, this is known as locally advanced cancer. The five-year survival rate is about 61 percent.
• Metastatic cancer: If the cancer has spread further to other parts of the body, it is known as metastatic cancer. The five-year survival rate is about 30 percent.

The overall five-year survival rate for anal cancer is about 66 percent.

Good to know: Survival rates do not predict what will happen to someone. Treatment and responses to treatment vary greatly.

Anal cancer FAQs

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1. AMBOSS. “Anal cancer.” 24 October 2017. Accessed 5 July 2018. ↩ ↩ ↩

2. Patient. “Anal Carcinoma. Information about Anal cancer.” 28 December 2017. Accessed 5 July 2018. ↩ ↩ ↩

3. URMC – University of Rochester. “Anal Cancer.” Accessed 5 July 2018. ↩ ↩ ↩

4. Cancer Stat Facts. “Anal Cancer.” Accessed 5 July 2018. ↩

5. Beating Bowel Cancer. “Anal Cancer – Types of Anal Cancer.” Accessed 2 July 2018. ↩ ↩

6. American Cancer Society. “What Is Anal Cancer?” 13 November 2017. Accessed 5 July 2018. ↩ ↩

7. Medscape eMedicine. “Anal Cancer Clinical Presentation.” 29 August 2017. Accessed 2 July 2018. ↩ ↩

8. NCBI. “The fraction of cancer attributable to modifiable risk factors.” 23 March 2018. Accessed 20 July 2018. ↩

9. Cancer.Net. “Anal Cancer: Diagnosis.” Accessed 5 July 2018. ↩

10. American Cancer Society. “Can Anal Cancer Be Found Early?” 13 November 2017. Accessed 20 July 2018. ↩ ↩

11. NCBI – NIH. “Screening for Anal Cancer in Women.” Accessed 20 July 2018. ↩

12. Cancer Research UK. “About anal cancer | Anal cancer.” Accessed 20 July 2018. ↩

13. American Cancer Society. “Surgery for Anal Cancer.” 13 November 2017. Accessed 20 July 2018. ↩

14. Anal Cancer Information. “Staging and Prognosis.” Accessed 20 July 2018. ↩

15. NCBI – NIH. “Anal cancer – a review.” Accessed 20 July 2018. ↩

16. Cancer.Net. “Anal Cancer: Statistics.” Accessed 20 July 2018. ↩

17. CTCA. “Pain Management for Anal Cancer Patients.” 29 June 2018. Accessed 20 July 2018. ↩

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