The anus is the canal that connects the lower part of the large intestine (the rectum) to the outside of the body. Anal cancer is fairly rare. Different cancers can develop in different parts of the anus, part of which is inside the body and part of which is outside. Sometimes abnormal changes of the anus are harmless in their early stages but may later develop into cancer. Some anal warts, for example, contain precancerous areas and can develop into cancer. The most common type of anal cancer is squamous cell carcinoma of the anus.
Symptoms of anal cancer
The symptoms of anal cancer may be:
Many of these symptoms may be caused by benign conditions e.g. haemorrhoids or and anal fissure, so thorough examination is important.
Stages of anal cancer
The 'stage' of the cancer defines whether the tumour is localised to the anus or whether it has spread to the local lymph nodes (usually the groin nodes or pelvic nodes) or whether it has spread to other organs. The treating oncologist needs to know the stage to decide the most suitable cancer treatment.
The information needed to decide the stage is gathered from both clinical examination and scanning. An examination under anaesthetic is often done to obtain the most accurate stage.
The stage is usually classified using a system called the 'TNM Staging System', where T stands for tumour, N for 'nodes' (ie lymph nodes), and M for 'metastases' (ie whether other organs are involved). Each letter is followed by a number that defines the extent of the cancer eg T2N1M0.
Diagnosis of anal cancer
The diagnosis is confirmed by taking a sample of the lump or suspicious region, and having this examined under a microscope by a specialist. The biopsy may be taken in the out-patient clinic, but usually a full examination of the area is undertaken whilst the patient is under anaesthetic. This allows a much more thorough examination to be done. The biopsy can be taken during this procedure.
Other tests that are done include a CT scan of the chest, abdomen and pelvis, and an MRI scan of the pelvis.
Treatment of anal cancer
Treatment for anal cancer is dependant on the stage of the disease and on the aim of the treatment. When the disease is localised it is potentially curable.
Anal cancer treatment options include surgery to remove the anus, or a combination of radiotherapy and chemotherapy given simultaneously. Specialised locally delivered radiotherapy (brachytherapy) has been used for very small anal tumours as well.
The usual treatment that is chosen is combination of chemotherapy and radiotherapy, called chemoradiotherapy. This cancer treatment has a major advantage over surgery in that most patients do not require a colostomy bag permanently. When surgery is performed with the aim of curing anal cancer, the anus itself is removed as well. With chemoradiotherapy, the organ is preserved. Another advantage of using chemoradiotherapy as the first treatment is that, surgery is still available as a curative treatment if the disease returns in the anus.
The radiotherapy is usually given on a daily basis, Monday to Friday, in a specialist department. It will involve lying still on a couch in a treatment room, whilst a treatment machine, gives the radiotherapy. The treatment does not hurt and is invisible. It does not make patient s radioactive. Each treatment lasts about fifteen minutes. Often, the bladder is kept full during the treatment to minimise the amount of radiotherapy given to the small bowel.
Before radiotherapy starts, there are a number of sessions that are undertaken to work out how to aim the radiotherapy to the areas that need to be treated. Often the first visit is to make sure the position is correct (sometimes lying on the front), and a specialised CT scan done with the patient in that position (this usually only takes 45 minutes to do). The scans are then worked on by the radiotherapy department, using sophisticated computer software, so as to get the best 'plan' for the treatment and the best treatment beam orientation. This can take 2 to 3 weeks to do. After a series of checks, the patient is given another appointment for a 'dummy run' of the treatment to make sure everything lines up accurately. The actual treatment then starts shortly afterwards.
The chemotherapy is usually given in the first and last week of the 5 and a half weeks of daily radiotherapy treatment. The chemotherapy may be given as an in-patient.
Chemoradiotherapy is a complex treatment and has many side effects. Most side effects disappear a few weeks after the treatment is completed, but some may last many months or be permanent.
The side effects of radiotherapy include:
The combination of the diarrhoea and the sore skin around the anus means that a temporary colostomy is sometimes recommended to make these side effects easier to manage.
These effects usually improve in the weeks after the treatment is completed, although the way the bowel works may not return to normal completely.
Side effects that may be long term or permanent include:
Vaginal narrowing and dryness: this can affect sexual function after treatment. It is important to see a specialist nurse before and during treatment who may advise using a vaginal dilator to minimise the risk of this side effect as much as possible.
Infertility: this should be discussed with the oncologist if it is an issue.
All the potential risks and side effects should be discussed by the oncologist.
Side effects of chemotherapy include:
nausea and vomiting: this can be reduced by anti-sickness medication given with the chemotherapy
sore mouth: mouthwashes can be given to help this
loss of appetite
a low blood count: if this happens, the body's defences against infection can be reduced, which in turn means any infection may become more serious.