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 to let stool pass out of the body. The anal canal, the part of the anus between the rectum and the anal opening, is about 1½ inches long.
The skin around the outside of the anus is called the perianal area. Tumors in this area are skin tumors, not anal cancer.

Being infected with the human papillomavirus (HPV) can affect the risk of developing anal cancer.

Risk factors include the following:
·         Being over 50 years old.
·         Being infected with human papillomavirus (HPV).
·         Having many sexual partners.
·         Having receptive anal intercourse (anal sex).
·         Frequent anal redness, swelling, and soreness.
·         Having anal fistulas (abnormal openings).
·         Smoking cigarettes.

Possible signs of anal cancer include bleeding from the anus or rectum or a lump near the anus.

These and other symptoms may be caused by anal cancer. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:
·         Bleeding from the anus or rectum.
·         Pain or pressure in the area around the anus.
·         Itching or discharge from the anus.
·         A lump near the anus.
·         A change in bowel habits.

Tests that examine the rectum and anus are used to detect (find) and diagnose anal cancer.

The following tests and procedures may be used:
·         Physical exam and 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.
·         Anoscopy: An exam of the anus and lower rectum using a short, lighted tube called an anoscope.
·         Proctoscopy: An exam of the rectum using a short, lighted tube called a proctoscope.
·         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 (chance of recovery) depends on the following:
·         The size of the tumor.
·         Where the tumor is in the anus.
·         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.
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 the 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, 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. For anal cancer, a CT scan of the pelvis and abdomen may be done.
·         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.

There are three ways that cancer spreads in the body.

The three ways that cancer spreads in the body are:
·         Through tissue. Cancer invades the surrounding normal tissue.
·         Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
·         Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.
When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.

The following stages are used for anal cancer:

Stage 0 (Carcinoma in Situ)

In stage 0, abnormal cells are found in the innermost lining of the anus. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.

Stage I

In stage I, cancer has formed and the tumor is 2 centimeters or smaller.

Stage II

In stage II, the tumor is larger than 2 centimeters.

Stage IIIA

In stage IIIA, the tumor may be any size and has spread to either:
·         lymph nodes near the rectum; or
·         nearby organs, such as the vagina, urethra, and bladder.

Stage IIIB

In stage IIIB, the tumor may be any size and has spread:
·         to nearby organs and to lymph nodes near the rectum; or
·         to lymph nodes on one side of the pelvis and/or groin, and may have spread to nearby organs; or
·         to lymph nodes near the rectum and in the groin, and/or to lymph nodes on both sides of the pelvis and/or groin, and may have spread to nearby organs.

Stage IV

In stage IV, the tumor may be any size and cancer may have spread to lymph nodes or nearby organs and has spread to distant parts of the body.

Recurrent Anal Cancer

Recurrent anal cancer is cancer that has recurred (come back) after it has been treated. The cancer may come back in the anus or in other parts of the body.

Treatment Option Overview

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:

Radiation therapy
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated.
Chemotherapy
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). When chemotherapy is placed directly into the spinal column, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). The way the chemotherapy is given depends on the type and stage of the cancer being treated.
Surgery
·         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 develop 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.

Having the human immunodeficiency virus can affect treatment of anal cancer.

Cancer therapy can further damage the already weakened immune systems of patients who have the human immunodeficiency virus (HIV). For this reason, patients who have anal cancer and HIV are usually treated with lower doses of anticancer drugs and radiation than patients who do not have HIV.

New types of treatment are being tested in clinical trials.

This 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 Web site.
Radiosensitizers
Radiosensitizers are drugs that make tumor cells more sensitive to radiation therapy. Combining radiation therapy with radiosensitizers may kill more tumor cells.

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.

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. This is sometimes called re-staging.
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 Options by Stage

For some types or stages of cancer, there may not be any trials listed. Check with your doctor for clinical trials that are not listed here but may be right for you.

Stage 0 (Carcinoma in Situ)

Treatment of stage 0 is usually local resection.

Stage I Anal Cancer

Treatment of stage I anal cancer may include the following:
·         Local resection.
·         External-beam radiation therapy with or without chemotherapy. If cancer remains after treatment, additional chemotherapy and radiation therapy may be given to avoid the need for a permanent colostomy.
·         Internal radiation therapy.
·         Abdominoperineal resection, if cancer remains or comes back after treatment with radiation therapy and chemotherapy.
·         Internal radiation therapy for cancer that remains after treatment with external-beam radiation therapy.
Patients 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.

Stage II Anal Cancer

Treatment of stage II anal cancer may include the following:
·         Local resection.
·         External-beam radiation therapy with chemotherapy. If cancer remains after treatment, additional chemotherapy and radiation therapy may be given to avoid the need for a permanent colostomy.
·         Internal radiation therapy.
·         Abdominoperineal resection, if cancer remains or comes back after treatment with radiation therapy and chemotherapy.
·         A clinical trial of new treatment options.
Patients 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.

Stage IIIA Anal Cancer

Treatment of stage IIIA anal cancer may include the following:
·         External-beam radiation therapy with chemotherapy. If cancer remains after treatment, additional chemotherapy and radiation therapy may be given to avoid the need for a permanent colostomy.
·         Internal radiation therapy.
·         Abdominoperineal resection, if cancer remains or comes back after treatment with chemotherapy and radiation therapy.
·         A clinical trial of new treatment options.

Stage IIIB Anal Cancer

Treatment of stage IIIB anal cancer may include the following:
·         External-beam radiation therapy with chemotherapy.
·         Local resection or abdominoperineal resection, if cancer remains or comes back after treatment with chemotherapy and radiation therapy. Lymph nodes may also be removed.
·         A clinical trial of new treatment options.

Stage IV Anal Cancer

Treatment of stage IV anal cancer may include the following:
·         Surgery as palliative therapy to relieve symptoms and improve the quality of life.
·         Radiation therapy as palliative therapy.
·         Chemotherapy with radiation therapy as palliative therapy.
·         A clinical trial of new treatment options.

Treatment Options for Recurrent Anal Cancer

Treatment of recurrent anal cancer may include the following:
·         Radiation therapy and chemotherapy, for recurrence after surgery.
·         Surgery, for recurrence after radiation therapy and/or chemotherapy.
·         A clinical trial of radiation therapy with chemotherapy and/or radiosensitizers.