Understanding anal cancer: from symptoms to treatment

Anal cancer refers to cancer that develops in the tissue at the end of your digestive tract, namely your anal canal. This cylinder of muscle makes up the last two to five centimetres of your digestive tract and keeps your back passage (rectum) closed until you are ready to open your bowels. 

Around 1,500 new cases of anal cancer are diagnosed every year in the UK, making it a rare type of cancer. 

Here we’ll look at risk factors, symptoms and treatments for anal cancer.

Risk factors for anal cancer

Anal cancer accounts for less than one percent of cancer cases in the UK. However, it is about twice as common in women as it is in men. 

The main risk factor for anal cancer is exposure to certain strains of human papillomavirus (HPV), specifically HPV 16, HPV 17 and HPV 18. Consequently, in women, a history of vulvar or cervical cancer, which can also be caused by HPV, increases the risk of anal cancer too. 

Other factors that increase your risk of anal cancer include smoking, conditions that affect your immune system (eg HIV and inflammatory bowel disease), a history of anal sex and increasing age. 

Symptoms of anal cancer

The main symptoms of anal cancer are rectal bleeding, blood in your stools, a change in your bowel habits (eg more frequent or less frequent bowel movements), a lump in your anal canal, and discomfort, pain and/or itching in your anus. 

You may also notice discharge from your rectum (ie mucus or pus) and/or pain in your groin area caused by swollen lymph nodes.

Types of anal cancer

There are several different types of anal cancer, which are grouped according to the type of cell in which they originate. 

The most common type of anal cancer, accounting for around nine out of every 10 cases, is squamous cell cancer. It can be caused by infection with HPV and starts in squamous cells that line the anal canal and the anal margin (the bottom part of the anal canal around the opening of the anus). 

There are several other types of anal cancer but these are very rare. 

Stages of anal cancer

Anal cancer is staged from one to four, according to how much the cancer has progressed:

• At stage 1, the tumour is less than two centimetres across and hasn’t spread to any nearby tissues
• At stage 2, the tumour is more than two centimetres across but still hasn’t spread to any nearby tissues
• At stage 3, the cancer has spread to nearby tissues or lymph nodes but not to distant organs or tissues
• At stage 4, also referred to as advanced anal cancer, the cancer has spread to other areas of the body, such as the liver

Getting a diagnosis

If you’ve noticed any of the symptoms of anal cancer mentioned earlier, it is important to see your GP. If anal cancer is present, the sooner it is detected and treated, the greater the chances of successful treatment.  

Your GP will ask you about your symptoms and medical history, and may perform a physical examination of your anus and rectum called a digital rectal examination (DRE). This will involve carefully passing a gloved, lubricated finger into your anus to feel for any lumps. 

Depending on your initial examination and any subsequent test results, you may need to have a tissue sample (biopsy) collected.

You may also need to have an imaging test of your chest, abdomen and pelvis, such as a CT scan or PET scan. 

Treating anal cancer

Treatment for anal cancer depends on the type and stage of anal cancer. It usually initially involves a combination of radiotherapy and chemotherapy (chemoradiotherapy). In some cases, no further treatment is needed. 

However, if chemoradiotherapy is not effective or the cancer returns, surgery may be needed to remove the affected part of the anus, or in more severe cases, the anus, rectum and part of the bowel. 

Depending on the extent of your surgery, you may need a temporary or permanent colostomy. A colostomy refers to a procedure to divert the end part of your bowel so that it exits through an opening (stoma) made into your abdomen. A special pouch is attached to the opening, into which your stools are collected. 

Living with a colostomy

If you need to have a colostomy, a special nurse called a stoma nurse will explain everything you need to know about living with a colostomy including: how to care for your stoma, how to empty and change the pouch, how to keep the area surrounding your stoma clean to help prevent any irritation or infection, how to reduce the risk of leaks and what equipment is available to help you feel more comfortable with your stoma. 

Living with a colostomy can be a major adjustment at first; however, the stoma and pouch are secure and safe to use, so you can engage in most of the activities you used to do before your colostomy. 

Most medications taken orally will still be effective with a colostomy but if you notice any tablets in your pouch or are otherwise concerned, speak to your GP or pharmacist. 

More advice and support about living with a colostomy is available from the UK charity, Colostomy UK.