What is Anal Cancer?

Around 343 Australians are diagnosed with anal cancer each year 

Anal cancer is a rare disease, affecting around 343 people a year in Australia (AIHW).  It is slightly more common in women than in men.
 
The outlook for anal cancer is often better than for other types of bowel cancer, especially when caught in the earlier stages.
 
The anus (back passage) is the 4 cm long end portion of the large bowel, which opens to allow solid waste to exit the body.  
 
Abnormal changes of the anus are sometimes harmless in their early stages, but may go on to develop into cancer.
 
Different cancers can develop in different parts of the anus.  Types of anal cancer include:
 
  • Squamous cell carcinomas
The most common type of anal cancer (about 75% of cases) is squamous cell carcinoma, which starts in the cells lining the anal margin and the anal canal.
 
The anal margin is the edge of the anus that can be partly seen as darker skin on the outside of the body and the anal canal is the part of the anus that is inside the body.  
 
The earliest form of squamous cell carcinoma is known as carcinoma in situ.
 
  • Adenocarcinomas
An estimated 15% of anal cancers are called adenocarcinomas.  
 
These affect glands in the anal area and one type of adenocarcinoma that can occur in the anal area, known as Paget's disease, can also affect the vulva, breasts, and other areas of the body.
 
Anal adenocarcinomas are usually treated in the same way as rectal cancer.
 
  • Skin cancers
A small number of anal cancers are either basal cell carcinomas, or malignant melanomas - two different types of skin cancer.
 
  • Other types of anal cancer
Other, very rare types of anal cancer are lymphomas, and gastrointestinal stromal tumours (GIST).
 

 
Causes and risk factors for Anal Cancer
 
The cause of anal cancer is still unknown, but there are several factors which may increase your risk of developing the disease.
 
The most common is the link to two specific 'oncogenic' (cancer causing) strains of HPV (human papilloma virus), an infection which causes genital and anal warts.
 
The following factors can put you at greater risk of developing anal cancer:
 
  • A history of cervical or vaginal cancer, or abnormal cells of the cervix, likely to be linked with HPV or smoking.

  • A lowered immune response as a result of another condition or treatment for other illnesses which suppress your immune system, such as HIV, or following organ transplantation.

  • Smoking tobacco has been shown to increase the risk of developing many cancers, including cancer of the anus.

  • Being infected with human papillomavirus (HPV).

  • Having receptive anal intercourse (anal sex).

  • Frequent anal redness, swelling, and soreness.

  • Having anal fistulas (abnormal openings).
Although rare, it is more prevalent in people over the age of 50, and in younger adults with HIV infection.
 
Some data suggests that people with a high lifetime number of sexual partners, are at higher risk.  This may be due to the increased risk of contracting HPV.
 
Unfortunately, some people get anal cancer for no clear reason.
 

 
Symptoms of Anal Cancer
 
The symptoms of anal cancer are very similar to other problems, including haemorrhoids (piles) or anal fissures (tears).
 
The most common symptom is rectal bleeding or blood in the stool (poo), with almost half of all patients affected in this way.
 
Other symptoms include:

  • Small lumps seen or felt around the anus which could be confused with piles.

  • An increase in the number or size of piles.

  • Pain in the anal area.

  • Difficulty in passing stools and extreme constipation are common symptoms.

  • Feeling a continuous urge to pass a motion, with no production, possibly with increased mucus.

  • Discharge from the back passage, or swelling, itching and persistent redness or soreness around the anal area.

  • Difficulty controlling your bowels (faecal incontinence).

  • One or more lumps in the groin area. 


 
Tests that examine the rectum and anus are used to detect 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.
 
Digital Rectum Exam (DRE)
 
  • 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 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.


 
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, such as the abdomen 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, computerised tomography, or computerised 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 (MRI).
 
  • 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
 
Cancer can spread through tissue, the lymph system, and the blood:
 
  • 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
 
When cancer spreads to another part of the body, it is called metastasis.  Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.
 
  • 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.
 

 
The following stages are used for anal cancer
 
About Bowel Cancer Tumour Sizes 770new
 
Tumor size compared to everyday objects; shows various measurements of a tumor compared to a pea, peanut, walnut, and lime.
 
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.
 

 
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 cerebrospinal fluid, 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 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.
About Anal Cancer Colostomy 770new

Three-panel drawing showing anal cancer surgery with colostomy; first panel shows area of anus with cancer, middle panel shows cancer and nearby tissue removed and stoma created, last panel shows a colostomy bag attached to the stoma.

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.
 


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.
 

 
Treatment Options by Stage
 
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, more 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, more 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, more 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 radiosensitisers.

Source: National Cancer Institute

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