Anal cancer is a relatively rare cancer that starts in the anus, the section of the large bowel through which solid waste passes out of the body.
Different cancers can develop in different parts of the anus. The most common type of cancer that affects the anal passage is squamous cell carcinoma and this accounts for approximately 90% of anal cancers. This type of cancer starts in the skin cells that line the anal area just outside the body or the anal canal.
Adenocarcinomas represent 10% of anal cancers. This type of cancer develops in the glands of the anus. Anal adenocarcinomas are usually treated the same way as rectal cancer. Other, very rare types of anal cancer are melanomas, gastrointestinal stromal tumours (GISTs) and lymphomas.
The symptoms of anal cancer can appear very similar to other conditions such as haemorrhoids but it’s important to see a doctor if they are unusual for you and do not go away.
They can include the following:
- Rectal bleeding is the most common symptom, and you may also notice blood in your faeces
- Severe itching which is a condition known as pruritus
- Changes to your bowel habits particularly constipation
- Pain and discomfort in your back passage
- The sensation of a lump around or in your anus or groin area or an increase in the size or number of piles
- Discharge, or mucus, from your rectum
However, approximately 20% of those diagnosed with anal cancer do not experience any symptoms.
Anal cancer is thought to affect over 1,400 people a year in the UK and is more common in women than men. Your risk of developing anal cancer can depend on many factors including your age and lifestyle factors:
- Human papilloma virus (HPV), the infection which cases genital and anal warts, is the biggest risk factor for anal cancer – around 90% of anal cancer cases are linked to HPV infection
- History of cervical or vaginal cancer or abnormal changes to cervical cells
- Being over 50
- Lowered immune response
Anal cancer often requires a different treatment pathway to colon or rectal cancer. You may be offered more than one of the following treatments – radiotherapy, chemotherapy, or surgery, often in combination.
For some small, stage one tumours surgery to remove the cancer may be advised as first step.
However for most patients, chemoradiotherapy is the first stage of treatment and for 90% of patients, this cures the cancer. For 10% of patients, they may need an operation known as a radical APER
If the cancer is metastatic either at diagnosis or after above treatments, chemotherapy is advised.
There is no screening programme for anal cancer and you may have one or more tests to determine whether you have anal cancer. This includes a physical examination of the rectum and you may also be given blood tests to check for anaemia and your general health. You may be referred for further diagnostic tests including a proctoscopy or colonoscopy where a thin tube is inserted to view the rectum and bowel.
Any abnormal lumps or tissues may be biopsied. CT and MRI scans may then be ordered.
Although anal cancers typically remain in the anal canal, they can spread to other areas of the body. The TNM system is used to assess what stage the cancer is and covers the size and location of the tumour, whether it’s spread to lymph nodes and whether it has metastasised to other organs.
In the initial, early stage, it is known as anal intraepithelial neoplasia (AIN) or Bowen’s disease, which may be treated with either topical creams or surgery. In stage one anal cancer, the cancer only affects the anus, is small in size and has not spread to the sphincter muscle. In stage two, it is bigger but still contained in the anal passage.
In stage three, it has spread to lymph nodes and nearby organs and in the final fourth stage, it has spread to more distant organs such as the liver or lungs.