Anal Cancer

FAQ's About Anal Cancer

What is Anal Cancer?

The anus is the final part of the digestive system. This sphincter (or opening) at the end of the digestive tract expels the body’s solid waste (poo). Anal cancer refers to cancer that affects the ‘anal canal’ and surrounding areas.

Anal cancer is relatively rare: in the UK there are only about 2,500 cases per year, although its incidence has been increasing over the past few decades.

Anal cancer survival rates are relatively good compared to some other cancers, especially when diagnosed early. However, survival rates can vary significantly depending on the stage at diagnosis and other factors like the person’s overall health.

What are the symptoms of Anal Cancer?

Symptoms of anal cancer can include bleeding from the anus, pain or a lump near the anus/bottom, itching, bleeding or discharge from the area. A person with Anal Cancer may also notice a change in bowel habits.

What causes Anal Cancer?

Anal Cancer can develop without a clear cause, but there are things that can increase risk:

Age – the risk of anal cancer increases with age, particularly in people over 50
Smoking – tobacco use is linked to a higher risk of developing anal cancer
Immune system – people who are on immunosuppression drugs, like organ transplant recipients, or those with a weakened immune system, such as people living with HIV
Other cancers – A history of cervical, vaginal or vulvar cancer

Anal Sex and Anal Cancer

While the vast majority of people who have anal sex won’t be diagnosed with anal cancer, the disease is slightly more common in people who engage in receptive anal intercourse (this includes cis women, trans women and men who have sex with men).

90% of anal cancers are linked to the Human Papillomavirus (HPV) infection. Around 50% of people carry HPV, but (for reasons that are not fully understood) there are a fraction of people who go on to develop cancer. HPV (in particular high-risk strains like HPV-16 and HPV-18) can lead to the development of pre-cancerous lesions known as Anal Intraepithelial Neoplasia (AIN).

Lower risk strains of HPV which cause anal warts (HPV-6 and HPV-11) and a history of transmitted infections from anal sex (STIs) are also linked to anal cancer.

Can you prevent Anal Cancer?

The HPV vaccine is highly effective in preventing anal cancer by targeting individuals before they are exposed to HPV. Whilst the vaccine is most effective when administered at a young age (offered to girls and boys around 12), it can still offer benefits for older individuals who have not yet been exposed to the virus.

Screening programs, such as anal Pap smears, have also been shown to help detect pre-cancerous changes early, especially in high-risk populations. Early detection of anal cancer can improve treatment outcomes significantly.

Diagnosing Anal Cancer

There are several tests that may be conducted if Anal Cancer is suspected. Usually when people are worried, they speak to their GP or they may seek help from a specialist sexual health clinic or service.

Initial diagnostics:

Digital Rectal Exam (DRE) – A healthcare professional inserts a gloved, lubricated finger into the rectum to feel for lumps and see how extensive it is and whether it is fixed to the surrounding tissues
Swabs – If a person is under the care of a sexual health clinic, a healthcare professional may take swabs to rule out a sexually transmitted infection

Further tests:

If Anal Cancer is suspected, the person will likely be sent for an endoscopic test to get a better look at the anus from the inside and also the rectum/colon too (these are the last parts of the digestive system, which connect to the anus).

Anoscopy – A small tube with a light (anoscope) is inserted into the anus to inspect for abnormal tissue
Proctoscopy – Similar to anoscopy but uses a slightly longer tube to examine deeper into the rectum
Sigmoidoscopy – A bigger but more flexible device is used to examines the rectum and into the colon to see if other abnormalities or risks are identified. Sometimes the symptoms of Anal Cancer are caused by issues higher up inside the bowel.

Once Anal Cancer has been diagnosed, further tests are needed to better understand the stage of a person’s cancer and how far it has spread into other parts of the body. Hospital doctors will conduct some or all of the following diagnostics:

CT Scan (Computed Tomography): Provides images of the anus to detect cancer spread (metastases), for example to the rectum
MRI (Magnetic Resonance Imaging): Detailed imaging to evaluate the tumour. MRI produces the clearest pictures; it will measure the tumour and how far it has spread to other tissues
PET Scan (Positron Emission Tomography): Identifies active cancer cells using a radioactive sugar tracer. This is particularly good for staging lymph nodes around the pelvis and will pick up additional disease in some cases, which is very important in treatment planning
Biopsy – A small sample of abnormal tissue is removed and analysed under a microscope to confirm the presence of cancer cells. The sample of cells can then be used to test for HPV (p16 test) and for molecular profiling to assess the ‘genetic fingerprint’ of the tumour
Full blood count, liver and kidney function – To help confirm the diagnosis, determine the cancer’s impact on the body and guide treatment planning

Are there different types of Anal Cancer?

Anal cancer is a less common type of cancer that develops in the tissues of the anus. The majority of anal cancers are squamous cell carcinomas, which arise from the thin, flat cells that line the anus. It can also develop in glandular tissues (adenocarcinoma), although this is less common. The rarest types of anal cancer are melanoma or sarcoma.

Doctors will be able to ‘stage’ squamous cell carcinoma cancers to guide the best treatment plan for a patient. Most cases of anal cancer are ‘staged’ using the TNM system. TNM stands for tumour, nodes, and metastases:

T describes how far the tumour has grown into the sphincter wall
N describes whether the cancer has spread to the lymph nodes
M describes whether the cancer has spread (metastasised) to other parts of the body

This system provides a detailed framework to assess cancer progression and guides treatment strategies.

T: Tumour size	N: Lymph Node Involvement	M: Distant metastasis?	Stage?
Tis: Carcinoma in situ (pre-cancerous, limited to surface layer of anus)	N0: No lymph node involvement	M0: No distant metastasis.	Stage 0: Tis, N0, M0.
T1: Tumour is 2 cm or smaller	N0: No lymph node involvement	M0: No distant metastasis.	Stage I: T1, N0, M0.
T2: Tumour is larger than 2 cm but 5 cm or smaller Or T3: Tumour is larger than 5 cm	N0: No lymph node involvement	M0: No distant metastasis	Stage II: T2–T3, N0, M0
T1 or T2	N1: Cancer has spread (N1a = to lymph nodes close to the anus N1b = to lymph nodes in groin or pelvis N1c = to both anal and groin/pelvic lymph nodes)	M0: No distant metastasis	Stage IIIA: T1–T2, N1, M0
T3: Tumour is larger than 5 cm Or T4: Tumour invades nearby organs (e.g., vagina, bladder, urethra)	N0 – N1	M0: No distant metastasis.	Stage IIIB: T3-T4, N0–N1, M0
T1 – T4	N1c	M0: No distant metastasis.	Stage IIIC: N1c, M0, (tumours can be any size T1-T4)
T1-4: Tumour is any size	N0-1C: Cancer has spread to no or many lymph nodes	M1: Cancer has spread to distant organs (e.g. liver)	Stage IV: Any T, Any N, M1.

Anal cancers are also ‘graded’ depending on how aggressive they look under the microscope, from those which look most similar to normal cells (these are referred to as ‘well differentiated’ or grade 1), moderately differentiated (grade 2) or poorly differentiated (grade 3). Grade 3 cancers are the most abnormal looking and tend to spread more quickly, which will affect the patient’s cancer treatment plan.

Dr Andrew Gaya is a Consultant Clinical Oncologist and one of the leading cancer doctors in Europe. He specialises in the treatment of gastrointestinal cancer.

If you are concerned about a recent diagnosis of Anal Cancer and want to speak with Dr Andy Gaya, click here to make an appointment.

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