Definition
Anal cancer is cancer of the anus. This is the canal at the end of the large intestine, below the rectum.
Cancer occurs when cells in the body (in this case the cells that cover the lumen of the anus) divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissues and spread to other parts of the body. A benign tumor does not invade or spread.
Causes
The exact cause of anal cancer is not clearly understood. But, there is evidence that human papillomavirus (HPV) causes many anal cancers.
Risk Factors
Risk factors include:
- Having receptive anal intercourse
- Having multiple sexual partners
- Having HPV infection
- Having HIV infection
- Receiving immunosuppressant drugs
- Being over 50 years old
- Smoking
- Having cervical dysplasia or cervical cancer
- Low CD4 count (cells that are part of the immune system)
Symptoms
If you have any of these symptoms, do not assume it is due to anal cancer. These symptoms may be caused by other conditions. Tell your doctor if you have any of these:
- Anal bleeding
- Pain or pressure around the anus
- Itching or discharge from the anus
- A lump near the anus
- Change in bowel habits (thinning in the width of the stool)
- Bleeding both with and without a bowel movement
Some anal cancers do not have symptoms.
Diagnosis
Your doctor will ask about your symptoms and medical history. He will also do a physical exam. Tests may include the following:
- Digital rectal examination
- Anoscopy—exam of the anus and lower rectum
- Proctoscopy—exam of the rectum
- Transrectal ultrasound—a probe is inserted into the anus and/or rectum so your doctor can view the internal tissues
- Biopsy —the removal of cells to test for cancer in a laboratory
- X-ray —a test that uses radiation to take a picture of structures inside the body
- CT scan —a type of x-ray that uses a computer to make pictures of structures inside the abdomen and pelvis
- PET scan —a test that makes images to show activity in body tissue
- Combined CT and PET scan
- MRI scan —a test that uses magnetic waves to make pictures of structures inside the body
- Lab tests—focusing on the function of the bone marrow, kidneys, and liver
Treatment
Talk with your doctor about the best treatment plan for you. Treatment options include the following:
Chemotherapy
In chemotherapy , drugs are used to kill cancer cells. Chemotherapy drugs travel through the bloodstream throughout the body to kill mostly cancer cells, but also some healthy cells. In the management of anal cancer, chemotherapy is given by vein, usually every three weeks during the course of daily radiation therapy.
Radiation Therapy
Radiation therapy is often delivered at the same time as chemotherapy. Compared to surgery, a combination of chemotherapy and radiation therapy can increase the survival rate.
In some cases, radiation therapy alone may be used if chemotherapy is thought to result in too many side effects (eg, in patients with HIV). In the treatment of anal cancer, radiation is delivered externally on a daily basis over 5-6 weeks.
Since radiation therapy damages healthy tissue as well as cancer cells, there are certain side effects associated with radiation therapy for the treatment of anal cancer. Scar tissue may form in the anus, keeping the anal sphincter from working properly. In addition, damage may occur that results in chronic rectal bleeding.
Surgery
Because of the location of the anus, an invasive cancer requires an abdominoperineal resection (APR). This surgery results in the formation of a permanent colostomy or bag. It is only considered if the cancer comes back after chemotherapy and radiation, or if radiation cannot be done for some reason.
Prevention
There are no known ways of avoiding anal cancer. You may be able to reduce your risk of anal cancer, though, by reducing your exposure to HIV and HPV. There is a vaccine available, called Gardasil, that protects against four types of HPV.
