Anal Cancer: Defining its Association With HPV

Anal cancer is a relatively rare type of cancer that starts in any part of the anus. It affects nearly 1,500 men and women in the UK every year, which is around 4 cases each day, and results in over 400 deaths annually¹. It has become more common over the past two decades in the UK, affecting relatively more women compared to men, and there is an increased risk in the older age groups. Infection with human papillomavirus (HPV) is strongly associated with anal cancer, as it is found in approximately 90% of cases in the UK.

Figure 1 Anatomy of the anal region showing the possible starting points of anal cancer – anal margin, anal canal, or transitional zone²

What is HPV?

HPV is a virus that primarily infects the skin and moist surfaces of the body (mucous membranes), including the genital area (cervix, vagina, vulva, penis, and anus), as well as the mouth and throat³. There are over 200 types of HPV, of which around 13 are classed as ‘high risk’ due to their potential to cause cancer, while the remaining are ‘low-risk’ types that do not cause cancer, with some associated with the development of warts on the hands, feet, or genitals. Globally, HPV is the most common sexually transmitted infection (STI). It is spread mainly through close skin-to-skin contact of the genital area, as well as during vaginal, anal, or  oral sex. Despite HPV infection affecting around 80% of people at some point in their lives⁴, the majority of people do not in fact experience any symptoms. Furthermore, the body’s immune system will usually clear the infection after a period of a couple of years without the affected individual being aware of the infection. However, infection with certain types of high-risk HPV, predominantly HPV types 16 and 18, can sometimes persist and potentially cause abnormal cell changes that may eventually develop into cancer^4,5.

Anal cancer: What are the signs and symptoms?

Anal cancer may not be associated with any signs or symptoms as in the case of 1 in 5 people who are diagnosed with the disease⁶. However, individuals who do experience symptoms may have any of the following: 

• Rectal bleeding: This is bleeding from the back passage, and represents one of the most common symptoms of anal cancer.
• Anal pain: Another quite common symptom is pain in or around the anus, which is occasionally associated with passing stool.
• Anal itching: Some people with anal pain may also experience anal itching in or around the anus. 
• Change in bowel habit: This includes problems controlling the emptying of bowels (bowel incontinence), the frequent urge to empty bowels, and passing loose stools.
• Mucus discharge: Mucus coming from the back passage can also be a sign of anal cancer. 
• Anal lump: In some cases of anal cancer, there is a sensation of a lump inside or around the anus which could give a feeling of wanting to open the bowels.
• Anal ulcer: Another possible symptom of anal cancer could be a non-healing anal sore (ulcer), which develops in or around the anus and may be painful.
• Weight loss: Unintentional or unexplained weight loss can also be a symptom of anal cancer.
• Fistula: Anal cancer can cause an abnormal connection (fistula) between the rectum and vagina possibly resulting in symptoms such as passing gas or stool from the vagina.

It is important to be aware that many of the above signs and symptoms are also caused by much more common conditions, such as haemorrhoids. Therefore, experiencing one or more of these symptoms does not necessarily mean that they are caused by anal cancer. However, it is still important to visit the GP especially if the symptoms persist or if there is ever any doubt or concern, in order to confirm the diagnosis and ensure that it is not related to a more serious health condition such as anal cancer. This is because diagnosing anal cancer at an early stage will result in a much more effective and successful treatment, and therefore significantly improving health outcomes.

Anal cancer: Treatment

Getting diagnosed with anal cancer is devastating as with any other type of cancer. Besides the physical aspect of the disease, there is also a huge emotional impact on the affected individual which often results in feelings of dread, confusion, hopelessness, and sadness. 

Thankfully, there are a number of treatment options available which can prove to be effective especially in the early stages of the disease. The choice of treatment will depend on the following⁷:

• Cancer size and location.
• Whether the cancer has spread.
• Patient’s general health status.

However, it is crucial to follow certain lifestyle changes prior to starting any treatment in order to improve feelings of control over both the physical and mental wellbeing in the long term. For this reason, there are certain pre-habilitation programmes that can be offered by the NHS for providing advice and support on different aspects prior to the start of cancer treatment such as diet, exercise, and mental health, as well as certain lifestyle habits including smoking and alcohol consumption. These interventions would later prove to be very useful while treatment is taking place and also during recovery, in addition to helping reduce the side effects often associated with treatment, and improving overall health and wellbeing⁸.

The main treatment for anal cancer involves a combination of radiotherapy and chemotherapy, called chemoradiation (or chemoradiotherapy)⁹. In radiotherapy, high-energy radiation is used to kill cancer cells; while in chemotherapy, certain drugs are taken to kill them. This combination forms the main treatment for anal cancer if it has not spread to other parts of the body, because chemotherapy helps make treatment with radiotherapy more effective by resulting in the cancer cells to become more ‘sensitive’ to treatment. Therefore, having both types of treatment together at the same time is often more effective than having either treatment type on its own. The treatment plan with chemoradiation usually involves 4 – 6 weeks of radiotherapy and 2 cycles of chemotherapy in the out-patient settings.

However, occasionally, surgery could be a necessary treatment option for anal cancer⁷. This is in the situation where:

• The cancer is at a very early stage.
• The combined therapy with chemoradiation has not been completely effective in getting rid of the cancer.

The type of surgery will depend on the stage of anal cancer (i.e. the extent or spread of the cancer within the body) along with the location of the cancer within the anus. Surgery usually involves removing only the affected part of the anus. 

However, if the cancer has spread or come back, surgery may be more extensive, and could involve the removal of the whole anus, the rectum (the part that joins the anus to the bowel), and even part of the bowel. In this situation, the patient will require a further surgical procedure called a ‘colostomy’ where part of the large bowel is brought to the surface of the abdomen to create an opening called a stoma, in order to allow stool to bypass the damaged or diseased section of the colon, and exit the body through the stoma into a collection bag¹⁰.

Chemoradiation has a better chance of treating anal cancer than surgery. It also avoids having a stoma which can have quite a significant impact on the patient’s quality of life.

Anal cancer: Prevention measures

Although there is no guaranteed measure for preventing anal cancer, there are a number of ways to reduce the risk of developing it and help protect against it. An effective preventative strategy against anal cancer involves a combination between the avoidance of risk factors and increasing protective factors.

Early detection

It is vital to be aware of the signs and symptoms of anal cancer, and knowing when to seek professional medical help when necessary. This is because early detection plays a crucial part in the successful treatment of anal cancer, and therefore improving health outcomes.

Healthy lifestyle

Making healthy lifestyle choices such as eating a balanced diet containing a variety of nutritious foods and antioxidant-rich fruits and vegetables helps to maintain healthy body weight, as well as reduce the overall risk of developing cancer and other chronic diseases. 

Additionally, engaging in regular physical exercise and avoiding certain negative lifestyle habits such as smoking and excessive alcohol consumption may also help reduce the overall risk of anal cancer.

HPV infection

Because the vast majority of anal cancers are caused by HPV, the preventative strategy must also include a specific focus on reducing the risk of an HPV infection. Although prevention of an HPV infection cannot be guaranteed either, there are certain things that can be done to help reduce the risk of infection, such as:

• Having good knowledge about HPV, including knowing how the virus is spread, its associated risk factors, and its potential health effects.
• Practising safe sex by using a condom, which can help reduce the risk of an HPV infection and anal cancer. However, it is important to be aware that this is not fully effective because the condom does not fully cover all of the skin, therefore HPV infection can still occur even with the use of barrier protection.
• Getting vaccinated against HPV, which is an effective way of offering protection against HPV infection. The most recent HPV vaccine covers 9 HPV types, and is part of a nationwide programme offered to children aged 12 to 13, as well as to people at higher risk of HPV infection such as men under 45 who have sex with men, sex workers, and people with HIV. However, despite the vaccine’s recognised effectiveness at helping protect against HPV infection and the related cancers, the protection that it offers against HPV is not complete because the vaccine does not cover all the high-risk types that are associated with cancer, including anal cancer.

There is no national screening programme for anal cancer in the UK¹¹. This is because, currently, there is no test available that can detect anal cancer at an early stage, as in the case of screening for cervical cancer.

10zyme: Advancing women’s health

We’re developing a groundbreaking self-test with instant results to detect the main cause of cervical cancer: high-risk HPV. Detecting infections early prevents cancer ever developing.

By enabling self-testing, we aim to empower women, overcome stigma and anxiety, and help eliminate a disease killing hundreds of thousands a year globally. See our Education Section to find out more.

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References:

1. Cancer Research UK (CRUK). (2015-2019). Anal cancer statistics. [Online]. Available at: https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/anal-cancer [Accessed 05/02/2024]
2. American Cancer Society. (2017). What Is Anal Cancer? [Online]. Available at: https://www.cancer.org/cancer/types/anal-cancer/about/what-is-anal-cancer.html [Accessed 15/02/2024]
3. National Health Service (NHS). (2022). Human papillomavirus (HPV). [Online]. Available at: https://www.nhs.uk/conditions/human-papilloma-virus-hpv/ [Accessed 15/02/2024]
4. Cancer Research UK (CRUK). (2024). Does HPV cause cancer? [Online]. Available at: https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/infections-eg-hpv-and-cancer/does-hpv-cause-cancer [Accessed 05/02/2024]
5. Choi S., Ismail, A., Pappas-Gogos, G., Boussios, S. (2023). HPV and Cervical Cancer: A Review of Epidemiology and Screening Uptake in the UK. Pathogens. 12(2): 298. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9960303/ [Accessed 15/02/2024]
6. Cancer Research UK (CRUK). (2022). Symptoms of anal cancer. [Online]. Available at: https://www.cancerresearchuk.org/about-cancer/anal-cancer/symptoms [Accessed 05/02/2024]
7. National Health Service (NHS). (2021). Treatment – Anal cancer. [Online]. Available at: https://www.nhs.uk/conditions/anal-cancer/treatment/ [Accessed 05/02/2024]
8. Cancer Research UK (CRUK). (2021). Preparing for treatment and life afterwards (prehabilitation). [Online]. Available at: https://www.cancerresearchuk.org/about-cancer/treatment/prehabilitation [Accessed 10/02/2024]
9. Macmillan Cancer Support. (2020). Chemoradiation for anal cancer. [Online]. Available at: https://www.macmillan.org.uk/cancer-information-and-support/treatments-and-drugs/chemoradiation-for-anal-cancer [Accessed 10/02/2024]
10. Macmillan Cancer Support. (2020). Surgery for anal cancer. [Online]. Available at: https://www.macmillan.org.uk/cancer-information-and-support/treatments-and-drugs/surgery-for-anal-cancer [Accessed 15/02/2024]
11. Cancer Research UK (CRUK). (2022). Screening for anal cancer. [Online]. Available at: https://www.cancerresearchuk.org/about-cancer/anal-cancer/getting-diagnosed/screening [Accessed 16/02/2024]