General Information About Anal Cancer
- Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus.
- Most anal cancers are related to human papillomavirus (HPV) infection.
- Signs of anal cancer include bleeding from the anus or rectum or a lump near the anus.
- Tests that examine the rectum and anus are used to diagnose anal cancer.
- Certain factors affect the prognosis (chance of recovery) and treatment options.
Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus.
The anus is the end of the large intestine, below the rectum, through which stool (solid waste) leaves the body. The anus is formed partly from the outer skin layers of the body and partly from the intestine. Two ring-like muscles, called sphincter muscles, open and close the anal opening and let stool pass out of the body. The anal canal, the part of the anus between the rectum and the anal opening, is about 1-1½ inches long. EnlargeAnatomy of the lower digestive system, showing the colon and other organs.
The skin around the outside of the anus is called the perianal area. 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.
Risk factors for anal cancer include the following:
Signs of anal cancer include bleeding from the anus or rectum or a lump near the anus.
- Bleeding from the anus or rectum.
- A lump near the anus.
- Pain or pressure in the area around the anus.
- Itching or discharge from the anus.
- A change in bowel habits.
Tests that examine the rectum and anus are used to diagnose anal cancer.
The following tests and procedures may be used:
- Physical exam and health history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
- Digital rectal examination (DRE): 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.EnlargeDigital 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: An exam of the anus and lower rectum using a short, lighted tube called an anoscope.
- Proctoscopy: 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: 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: 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.
Certain factors affect the prognosis (chance of recovery) and treatment options.
The prognosis depends on the following:
- The size of the tumor.
- Whether the cancer has spread to the lymph nodes.
The treatment options depend on the following:
- The stage of the cancer.
- Where the tumor is in the anus.
- Whether the patient has human immunodeficiency virus (HIV).
- Whether cancer remains after initial treatment or has recurred.
Stages of Anal Cancer
- 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.
- There are three ways that cancer spreads in the body.
- Cancer may spread from where it began to other parts of the body.
- The following stages are used for anal cancer:
- Stage 0
- Stage I
- Stage II
- Stage III
- Stage IV
- Anal cancer can recur (come back) after it has been treated.
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): A procedure that makes a series of detailed pictures of areas inside the body, such as the abdomen, pelvis, or chest, taken from different angles. The pictures are made by a computer linked to an x-ray machine. 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: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
- MRI (magnetic resonance imaging): 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): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
- Pelvic exam: 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.EnlargePelvic 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.
There are three ways that cancer spreads in the body.
- Tissue. The cancer spreads from where it began by growing into nearby areas.
- Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.
- Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.
Cancer may spread from where it began to other parts of the body.
- Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.
- Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.
The metastatic tumor is the same type of cancer as the primary tumor. For example, if anal cancer spreads to the lung, the cancer cells in the lung are actually anal cancer cells. The disease is metastatic anal cancer, not lung cancer.
Many cancer deaths are caused when cancer moves from the original tumor and spreads to other tissues and organs. This is called metastatic cancer. This animation shows how cancer cells travel from the place in the body where they first formed to other parts of the body.
The following stages are used for anal cancer:
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 squamous intraepithelial lesion (HSIL).
EnlargeTumor 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 II anal cancer is divided into stages IIA and IIB.
- In stage IIA, the tumor is larger than 2 centimeters but not larger than 5 centimeters.
- In stage IIB, the tumor is larger than 5 centimeters.
Stage III anal cancer is divided into stages IIIA, IIIB, and IIIC.
- In stage IIIA, the tumor is 5 centimeters or smaller and has spread to lymph nodes near the anus or groin.
- 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.
Anal cancer can recur (come back) after it has been treated.
The cancer may come back in the anus or other parts of the body, such as the liver or lungs.
Treatment Option Overview
- There are different types of treatment for patients with anal cancer.
- Three types of standard treatment are used:
- Radiation therapy
- New types of treatment are being tested in clinical trials.
- Treatment for anal cancer may cause side effects.
- Patients may want to think about taking part in a clinical trial.
- Patients can enter clinical trials before, during, or after starting their cancer treatment.
- Follow-up tests may be needed.
There are different types of treatment for patients with anal cancer.
Different types of treatments are available for patients with anal cancer. Some treatments are standard (the currently used treatment), and some 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. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment. Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Three types of standard treatment are used:
- Local resection: 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 patient can still control bowel movements. Tumors that form in the lower part of the anus can often be removed with local resection.
- Abdominoperineal resection: 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.EnlargeResection 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.
The way the radiation therapy is given depends on the type and stage of the cancer being treated. External and internal radiation therapy are used to treat anal cancer.
Chemotherapy is a cancer treatment that 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).
New types of treatment are being tested in clinical trials.
This summary section describes treatments that are being studied in clinical trials. It may not mention every new treatment being studied. Information about clinical trials is available from the NCI website.
Radiosensitizers are drugs that make tumor cells more sensitive to radiation therapy. Combining radiation therapy with radiosensitizers may kill more tumor cells.
Immunotherapy is a treatment that uses the patient’s immune system to fight cancer. Substances made by the body or made in a laboratory are used to boost, direct, or restore the body’s natural defenses against cancer. This type of cancer treatment is also called biotherapy or biologic therapy.
Immune checkpoint inhibitor therapy is a type of immunotherapy.
- Immune checkpoint inhibitor therapy: PD-1 is a protein on the surface of T cells that helps keep the body’s immune responses in check. When PD-1 attaches to another protein called PDL-1 on a cancer cell, it stops the T cell from killing the cancer cell. PD-1 inhibitors attach to PDL-1 and allow the T cells to kill cancer cells. Pembrolizumab and nivolumab are types of immune checkpoint inhibitors.
EnlargeImmune checkpoint inhibitor. Checkpoint proteins, such as PD-L1 on tumor cells and PD-1 on T cells, help keep immune responses in check. The binding of PD-L1 to PD-1 keeps T cells from killing tumor cells in the body (left panel). Blocking the binding of PD-L1 to PD-1 with an immune checkpoint inhibitor (anti-PD-L1 or anti-PD-1) allows the T cells to kill tumor cells (right panel).Immunotherapy uses the body’s immune system to fight cancer. This animation explains one type of immunotherapy that uses immune checkpoint inhibitors to treat cancer.
Treatment for anal cancer may cause side effects.
Patients may want to think about taking part in a clinical trial.
For some patients, taking part in a clinical trial may be the best treatment choice. Clinical trials are part of the cancer research process. Clinical trials are done to find out if new cancer treatments are safe and effective or better than the standard treatment.
Many of today’s standard treatments for cancer are based on earlier clinical trials. Patients who take part in a clinical trial may receive the standard treatment or be among the first to receive a new treatment.
Patients who take part in clinical trials also help improve the way cancer will be treated in the future. Even when clinical trials do not lead to effective new treatments, they often answer important questions and help move research forward.
Patients can enter clinical trials before, during, or after starting their cancer treatment.
Some clinical trials only include patients who have not yet received treatment. Other trials test treatments for patients whose cancer has not gotten better. There are also clinical trials that test new ways to stop cancer from recurring (coming back) or reduce the side effects of cancer treatment.
Clinical trials are taking place in many parts of the country. Information about clinical trials supported by NCI can be found on NCI’s clinical trials search webpage. Clinical trials supported by other organizations can be found on the ClinicalTrials.gov website.
Follow-up tests may be needed.
Some of the tests that were done to diagnose the cancer or to find out the stage of the cancer may be repeated. Some tests will be repeated in order 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). These tests are sometimes called follow-up tests or check-ups.
Treatment of Stage 0 (Carcinoma in Situ)
Treatment of Stages I, II, and III Anal Cancer
Treatment of Stage IV Anal Cancer
Treatment of HIV and Anal Cancer
In general, treatment for patients who have anal cancer and the human immunodeficiency virus (HIV) is similar to treatment for other patients, and these patients have similar outcomes. However, this treatment can further damage the weakened immune systems of patients who have HIV. Treatment in patients 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.
Treatment of Recurrent Anal Cancer
To Learn More About Anal Cancer
For general cancer information and other resources from the National Cancer Institute, see the following:
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