Patient Information from National Cancer Institute
Anal cancer is a rare disease, affecting around 435 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.
Types of anal cancer
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.
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 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.
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, 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 are used to detect and diagnose anal cancer
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.
After anal cancer has been diagnosed, how is anal cancer staged?
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.
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.
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 cm or smaller.
Stage II
In stage II, the tumor is larger than 2 cm.
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.
There are different types of treatment for patients with anal cancer
Different types of treatments are available for patients with anal cancer. 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.
Dr Jennifer Liang 