Anal Cancer

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.

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The skin around the outside of the anus is called the peri-anal area. Tumors in this area are skin tumors, not anal cancer.

Risk Factors

  • Being over 50
  • Being infected with human papillomavirus (HPV)
  • Having multiple sexual partners
  • Having receptive anal intercourse
  • Frequent anal redness, swelling, and soreness.
  • Having anal fistulas (abnormal openings)
  • Tobacco Use

Signs and Symptoms

  • 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.

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Diagnosis

  • 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.

Prognosis

The prognosis (chance of recovery) depends on:

  • The size of the tumor. 
  • Where the tumor is in the anus. 
  • Whether the cancer has spread to the lymph nodes. 

Staging Anal Cancer

The process used to find out if cancer has spread within the anus or to other parts of the body is called staging and  determines the stage of the disease. It is important to know the stage in order to plan treatment. The following tests may be used to stage anal cancer:

  • 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.
  • 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.

How Cancer Spreads in the Body

  • 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.

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Stages of Anal Cancer

  • 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.

 Sarcoma Sizes

Pea, peanut, walnut, and lime show tumor sizes.
Image courtesy of http://teresewinslow.com 

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

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

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.

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.

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.

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Treatment
 

Standard vs. Experimental

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.

Factors Influencing Treatment

  • 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.

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

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.

Impact of HIV Status on Treatment

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.

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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

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.

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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 Web site.

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

Followup Tests

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.

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Treatment Options by Stage


Stage 0 Anal Cancer

  • Usually local resection.

Stage I Anal Cancer

  • 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

  • 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.

Stage IIIA Anal Cancer

  • Abdominoperineal resection, if cancer remains or comes back after treatment with chemotherapy and radiation therapy.

Stage IIIB Anal Cancer

  • 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.

Stage IV Anal Cancer

  • 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.

Treatment Options for Recurrent Anal Cancer

  • 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.

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