Anal cancer is a type of cancer that forms in the tissues of the anus.
The anus is the end of the large intestine. It is where stool (solid waste) leaves the body. The anus is formed partly from the outer skin layers of the body and partly from the intestine. The anus is connected to the rectum by the anal canal, which is about 1 to 1½ inches long. This area is controlled by two ring-like sphincter muscles, which contract to hold stool in and relax to allow its passage out of the body.
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Anatomy of the lower gastrointestinal (digestive) system showing the colon, rectum, and anus. Other organs that make up the digestive system are also shown.
Anal cancer can start in the lining of the anal canal, called the mucosa, or in the perianal skin, the squamous cells outside of the anus that contain hair follicles and sweat glands.
Tumors of the perianal skin that do not involve the anal sphincter are usually treated the same as anal cancers, although local therapy (treatment directed to a limited area of skin) may be used for some.
Most anal cancers are related to human papillomavirus (HPV) infection.
Anal cancer is caused by certain changes to the way blood stem cells function, especially how they grow and divide into new cells. A risk factor is anything that increases the chance of getting a disease. Some risk factors for anal cancer can be changed. However, risk factors also include things people cannot change, like their genetics, getting older, and their health history.
There are many risk factors for anal cancer, but many do not directly cause cancer. Instead, they increase the chance of DNA damage in cells that may lead to anal cancer. To learn more about how cancer develops, see What Is Cancer?
Having one or more of these risk factors does not mean that you will get anal cancer. Many people with risk factors never develop anal cancer, while others with no known risk factors do.
Digital rectal examination (DRE) is an exam of the anus and rectum. The doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for lumps or anything else that seems unusual.
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Digital rectal exam (DRE). The doctor inserts a gloved, lubricated finger into the rectum and feels the rectum, anus, and prostate (in males) to check for anything abnormal.
Anoscopy is an exam of the anus and lower rectum using a short, lighted tube called an anoscope.
Proctoscopy is a procedure to look inside the rectum and anus to check for abnormal areas, using a proctoscope. A proctoscope is a thin, tube-like instrument with a light and a lens for viewing the inside of the rectum and anus. It may also have a tool to remove tissue samples, which are checked under a microscope for signs of cancer.
Endo-anal or endorectal ultrasound is a procedure in which an ultrasound transducer (probe) is inserted into the anus or rectum and used to bounce high-energy sound waves (ultrasound) off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.
Biopsy is the removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer. If an abnormal area is seen during the anoscopy, a biopsy may be done at that time.
After anal cancer has been diagnosed, tests are done to find out if cancer cells have spread within the anus or to other parts of the body.
The process used to find out if cancer has spread within the anus or to other parts of the body is called staging. The information gathered from this staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. The following tests may be used in the staging process:
CT scan (CAT scan) uses a computer linked to an x-ray machine to make a series of detailed pictures of areas inside the body, such as the abdomen, pelvis, or chest. The pictures are taken from different angles and are used to create 3-D views of tissues and organs. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
Chest x-ray is a type of radiation that can go through the body and make pictures of the organs and bones inside the chest.
MRI (magnetic resonance imaging) is a procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).
PET scan (positron emission tomography scan) uses a small amount of radioactive glucose that is injected into a vein. The PET scanner rotates around the body and makes pictures of where glucose is being used in the body. Cancer cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
Pelvic exam is an exam of the vagina, cervix, uterus, fallopian tubes, ovaries, and rectum. A speculum is inserted into the vagina and the doctor or nurse looks at the vagina and cervix for signs of disease. A Pap test of the cervix is usually done. The doctor or nurse also inserts one or two lubricated, gloved fingers of one hand into the vagina and places the other hand over the lower abdomen to feel the size, shape, and position of the uterus and ovaries. The doctor or nurse also inserts a lubricated, gloved finger into the rectum to feel for lumps or abnormal areas.
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Pelvic exam. A doctor or nurse inserts one or two lubricated, gloved fingers of one hand into the vagina and presses on the lower abdomen with the other hand. This is done to feel the size, shape, and position of the uterus and ovaries. The vagina, cervix, fallopian tubes, and rectum are also checked.
Some people decide to get a second opinion.
You may want to get a second opinion to confirm your anal cancer diagnosis and treatment plan. If you seek a second opinion, you will need to get medical test results and reports from the first doctor to share with the second doctor. The second doctor will review the pathology report, slides, and scans. They may agree with the first doctor, suggest changes or another treatment approach, or provide more information about your cancer.
Cancer stage describes the extent of cancer in the body, such as the size of the tumor, whether it has spread, and how far it has spread from where it first formed. It is important to know the stage of the anal cancer to plan the best treatment.
There are several staging systems for cancer that describe the extent of the cancer. Anal cancer staging usually uses the TNM staging system. The cancer may be described by this staging system in your pathology report. Based on the TNM results, a stage (I, II, III, or IV, also written as 1, 2, 3, or 4) is assigned to your cancer. When talking to you about your diagnosis, your doctor may describe the cancer as one of these stages.
In stage 0, abnormal cells are found in the mucosa (innermost layer) of the anus. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called high-grade intraepithelial lesion (HSIL).
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Tumor sizes are often measured in centimeters (cm) or inches. Common food items that can be used to show tumor size in cm include: a pea (1 cm), a peanut (2 cm), a grape (3 cm), a walnut (4 cm), a lime (5 cm or 2 inches), an egg (6 cm), a peach (7 cm), and a grapefruit (10 cm or 4 inches).
Stage I (also called stage 1) anal cancer
In stage I, cancer has formed and the tumor is 2 centimeters or smaller.
In stage IIIB, the tumor is any size and has spread to nearby organs, such as the vagina, urethra, or bladder. Cancer has not spread to lymph nodes.
In stage IIIC, the tumor is any size and may have spread to nearby organs. Cancer has spread to lymph nodes near the anus or groin.
Stage IV (also called stage 4) anal cancer
In stage IV, the tumor is any size. Cancer may have spread to lymph nodes or nearby organs and has spread to other parts of the body, such as the liver or lungs.
Stage IV anal cancer is also called metastatic anal cancer. Metastatic cancer happens when cancer cells travel through the lymphatic system or blood and form tumors in other parts of the body. The metastatic tumor is the same type of cancer as the primary tumor. For example, if anal cancer spreads to the liver, the cancer cells in the liver are actually anal cancer cells. The disease is called metastatic anal cancer, not liver cancer. Learn more in Metastatic Cancer: When Cancer Spreads.
Anal cancer can recur (come back) after it has been treated.
Recurrent anal cancer is cancer that has come back after it has been treated. If anal cancer comes back, it may come back in the anus or in other parts of the body, such as the liver or lungs. Tests will be done to help determine where the cancer has returned. The type of treatment for recurrent anal cancer will depend on where it has come back.
There are different types of treatment for people with anal cancer.
Different types of treatments are available for anal cancer. You and your cancer care team will work together to decide your treatment plan, which may include more than one type of treatment. Many factors will be considered, such as the stage of the cancer, your overall health, and your preferences. Your plan will include information about your cancer, the goals of treatment, your treatment options and the possible side effects, and the expected length of treatment.
Talking with your cancer care team before treatment begins about what to expect will be helpful. You’ll want to learn what you need to do before treatment begins, how you’ll feel while going through it, and what kind of help you will need. To learn more, visit Questions to Ask Your Doctor about Treatment.
The following types of treatment are used:
Surgery
Local resection is a surgical procedure in which the tumor is cut from the anus along with some of the healthy tissue around it. Local resection may be used if the cancer is small and has not spread. This procedure may save the sphincter muscles so the person can still control bowel movements. Tumors that form in the lower part of the anus can often be removed with local resection.
Abdominoperineal resection is a surgical procedure in which the anus, the rectum, and part of the sigmoid colon are removed through an incision made in the abdomen. The doctor sews the end of the intestine to an opening, called a stoma, made in the surface of the abdomen so body waste can be collected in a disposable bag outside of the body. This is called a colostomy. Lymph nodes that contain cancer may also be removed during this operation. This procedure is used only for cancer that remains or comes back after treatment with radiation therapy and chemotherapy.
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Resection of the colon with colostomy. Part of the colon containing the cancer and nearby healthy tissue are removed, a stoma is created, and a colostomy bag is attached to the stoma.
Radiation therapy
Radiation therapy uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy used to treat anal cancer:
External radiation therapy uses a machine outside the body to send radiation toward the area of the body with cancer.
Chemotherapy (also called chemo) uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy).
Chemotherapy drugs used to treat anal cancer include:
New types of treatment are being tested in clinical trials.
A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. For some patients, taking part in a clinical trial may be an option.
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. Clinical trials supported by other organizations can be found on the ClinicalTrials.gov website.
This summary section describes treatments that are being studied in clinical trials. It may not mention every new treatment being studied.
Radiosensitizers
Radiosensitizers are drugs that make tumor cells more sensitive to radiation therapy. Combining radiation therapy with radiosensitizers may kill more tumor cells.
Immunotherapy
Immunotherapy helps a person’s immune system fight cancer. Your doctor may suggest biomarker tests to help predict your response to certain immunotherapy drugs. Learn more about Biomarker Testing for Cancer Treatment.
Immunotherapy drugs being studied in the treatment of anal cancer include:
As you go through treatment, you will have follow-up tests or check-ups. Some tests that were done to diagnose or stage the cancer may be repeated to see how well the treatment is working. Decisions about whether to continue, change, or stop treatment may be based on the results of these tests.
Some of the tests will continue to be done from time to time after treatment has ended. The results of these tests can show if your condition has changed or if the cancer has recurred (come back).
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
abdominoperineal resection, if cancer remains or comes back after treatment with radiation therapy and chemotherapy, or other options that may include treatment with additional chemoradiation therapy, chemotherapy alone, or immunotherapy
Those who have had treatment that saves the sphincter muscles may receive follow-up exams every 3 months for the first 2 years, including rectal exams with endoscopy and biopsy, as needed to check for recurrence.
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
Treatment of HIV and Anal Cancer
In general, treatment for people who have anal cancer and HIV is similar to treatment for other people, and these patients have similar outcomes. However, this treatment can further damage the weakened immune systems of people who have HIV. Treatment for people with a history of AIDS-related complications may require lower doses of anticancer drugs and radiation therapy than doses used for patients who do not have HIV.
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.
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This PDQ cancer information summary has current information about the treatment of anal cancer. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.
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Clinical trials can be found online at NCI's website. For more information, call the Cancer Information Service (CIS), NCI's contact center, at 1-800-4-CANCER (1-800-422-6237).
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PDQ® Adult Treatment Editorial Board. PDQ Anal Cancer Treatment. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/anal/patient/anal-treatment-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389368]
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