Anal Cancer
What is Anal Cancer?
Cancer occurs where normal cells in the body, through genetic changes, lose the ability to control and regulate growth. As cancers grow, they can invade tissue around them (local invasion). Through further genetic changes, cancers can also spread more widely, often first to local lymph nodes then to distant organs such as the liver or lungs. These are known as metastases or secondaries.
Anal cancers arise from cells at the anal opening (anal verge) or just within the anal canal. Most arise from squamous cells and are called squamous cell carcinomas (SCC).
How common is Anal Cancer?
Anal cancers are not common, making up just 1% of gastrointestinal cancers. The incidence is around 1 case per 100,000 people.
Who is at risk?
Anal cancer is preceded by changes in the lining of the anus known as anal intraepithelial neoplasia (AIN). This is usually caused by infection with human papilloma virus (HPV), and is similar to the changes in the cervix (CIN) that lead to cervical cancer in women.
The risk factors for anal cancer include:
- HPV infection
- Age (most people are over age 50)
- Anal warts (also caused by HPV)
- Cervical lesions including CIN and cervical cancer (also due to HPV)
- Anal sex
- Smoking
- Immunosuppression (a condition or medications that suppress the immune system such as after organ transplantation or HIV infection)
- Chronic inflammation (such as chronic anal fistula) may slightly increase the risk
- Pelvic radiation
Can Anal Cancer be prevented?
Few cancers can be totally prevented but it is likely that vaccination against HPV virus will protect many people from developing anal cancer. Using condoms will not eliminate the risk but will reduce it. Stopping smoking will reduce the risk of many cancers including anal caner.
What are the symptoms?
Anal cancer is often diagnosed early when patients see their doctor with symptoms. The symptoms of anal cancer are not specific for anal cancer but should prompt a check-up with the local doctor.
These include:
- Bleeding from the anus
- A lump or mass at the anus
- A sensation that the bowels have not completely emptied after passing stool
- Anal pain
- Anal itch or discharge
- Change in bowel habits
Can Anal Cancer be prevented?
Usually, a surgeon will organise a biopsy under an anaesthetic to confirm the diagnosis. If you have swollen lymph nodes in the groin, a biopsy using ultrasound guidance may also be performed. This will usually be followed by some tests to assess the cancer and see if it is localised to the anus. These may include an MRI, a CT scan and a PET scan.
What are the treatment options?
There are 3 types of treatment used for anal cancer; radiation, chemotherapy and surgery. Most cancers will be treated with a combination of radiation therapy and chemotherapy. Occasionally, a small cancer may be removed with surgery with a local excision. Sometimes surgery will be required after radiotherapy/chemotherapy if the cancer is still present or comes back.
Will I need a stoma?
Most patients treated with anal cancer will not need a stoma. For those patients who are not cured with radiotherapy/chemotherapy, removal of the anus and rectum with formation of a stoma will usually be required. This is known as abdomino-perineal resection (APR).
What are the prospects of cure?
Many patients will be cured of anal cancer with combination therapy with radiation/chemotherapy. Approximately 3 in 10 patients will need surgery after combination treatment. For patients that undergo surgery, approximately half will be alive 5 years after surgery.
What is the follow up after treatment?
Your surgeon will arrange a schedule of follow-up that will extend for many years after treatment of your cancer. This helps to identify problems that may arise and identify recurrent disease early. Follow up will include examination in the rooms and sometimes under anaesthetic, colonoscopy and imaging such as MRI, CT and PET scans.