Anal cancer is a form of bowel cancer. However, anal cancer accounts for only two percent of all cases of colon cancer. This makes it one of the rarer malignant tumors of the bowel. Every year, around one in 500,000 people are diagnosed with anal canal or anal cancer.
Anal canal carcinoma predominantly affects women, while men are more likely to develop anal verge carcinoma. Most anal carcinomas occur after the age of 60.
The exact causes of anal cancer are not entirely clear. However, there are various risk factors that can promote the degeneration of cells in the bowel. These include, in particular, damage to the skin in the anal area. This can be caused, for example, by chronic inflammatory bowel diseases (IBD) such as Crohn's disease or ulcerative colitis.
An infection with human papillomaviruses (HPV) is also associated with the development of anal carcinoma. The pathogens are among the most frequently sexually transmitted viruses. Up to 85 percent of all patients with anal cancer are infected with the papilloma viruses. In particular, high-risk types such as HPV 16, 18, 31 and 33 lead to carcinoma via various intermediate stages, the so-called precancerous stages.
Papilloma viruses are mainly transmitted during unprotected sexual intercourse. Therefore, passive (receptive) anal intercourse is another important risk factor. The risk of infection increases during sexual intercourse with frequently changing sexual partners.
A weakened immune system can also make the development of cancer more likely. The body cannot defend itself sufficiently against pathogens or developing tumor cells. HIV and AIDS patients as well as other people with a weakened immune system therefore have an increased risk of developing anal cancer.
Smoking is also a risk factor for anal cancer.
Tumors that form on the anal verge or anal canal are rather rare © bilderzwerg | AdobeStock
Anal cancer can cause various symptoms. They are usually so unspecific that a possible cancer is quickly overlooked. In many patients, however, there are blood deposits on the stool. Pain during bowel movements and excruciating itching in the anal area can also indicate a tumor. Depending on the size of the tumor, patients may also feel a foreign body sensation.
If the tumor constricts the anal canal, the faeces can become deformed. Indentations or very thin stools are typical here. This is also known as pencil stool due to its characteristic shape.
Stool irregularities may also occur. These include
Patients are not always able to control their bowel movements and therefore suffer from faecal incontinence.
In addition, there are often non-specific general symptoms. These include
- Fatigue and tiredness,
- weight loss,
- night sweats and
- enlarged lymph nodes in the groin.
When it comes to treatment, medicine distinguishes between anal margin tumors and anal canal carcinomas. Anal margin tumors have a more favourable prognosis overall.
The method of choice and standard treatment is complete surgical removal of the tumor. To ensure that no cancer cells remain in the anal area, a safety margin of one centimeter is usually maintained.
In order to enable patients to live as pain-free a life as possible after the operation, one of the aims of the operation is to maintain bowel continence. If there is a risk of faecal incontinence as a result of the operation, radiotherapy can be carried out as an alternative.
The tumor can also be treated with radiochemotherapy before the operation. The aim of this so-called neoadjuvant therapy is to shrink the tumor. Many patients are spared an artificial anus praeter (anus praeter) due to the upstream radiochemotherapy.
Radiotherapeutic measures are also used if the regional lymph nodes are affected. In most cases, however, these are first surgically removed in a radical lymphadenectomy.
Carcinomas of the anal canal are mainly treated with combined radiochemotherapy. This involves radiotherapy of the tumor area and the lymph nodes in the pelvic and groin area. This radiotherapy usually lasts between five and seven weeks.
Patients receive chemotherapy at the same time. In most cases, the cytostatic drugs 5-FU (5-fluorouracil) and mitomycin C are used. These drugs are intended to inhibit cell growth and thus kill the fast-growing cells of anal canal carcinoma. The chemotherapeutic agents are administered via a port that is placed under the skin.
Chemotherapeutic agents are also used for the palliative treatment of inoperable metastatic anal cancers.
In the case of an inoperable tumor, the narrowing of the anal canal can also be treated with cryosurgery or laser in some cases.
Palliative therapy is intended to improve the patient's quality of life if a cure is no longer possible.
Inpatient rehabilitation can be offered for
- Fecal incontinence,
- consequential damage caused by radiotherapy or
- for patients with an artificial bowel outlet
may be useful.
Five years after the initial diagnosis, between 70 and 90 percent of patients are still alive.
After successful treatment, clinical examinations are carried out every three months for the first two years to rule out recurrence. Recurrence is defined as a recurrence of the tumor.
