Anal Cancer: Treatment and Screening Tests

Cancer that starts from the anal canal, the short tube at the end of the rectum, is called anal cancer. This uncommon type of cancer accounts for about 1-2% of all cancers of the intestines. It is often localized in the anal canal. However, it sometimes spreads to the liver and lungs, making it extremely difficult to treat. Based on the place of origin, anal cancer is divided into two types:

· Cancers of the anal canal (above the anal verge)

· Cancers of the perianal skin (below the anal verge)

The anal mucosa usually undergoes some changes. While some of these changes are innocuous, others may turn into cancer with time. Such changes are called pre-cancer or dysplasia. Benign growths of the tissues and cells in the anal canal, such as polyps, skin tags, and anal warts, are some examples of innocuous outgrowths (benign) that might turn into tumors under favorable conditions.

Anal Cancer Causes

While the exact cause of anal cancer is unknown, several factors contributing to its development have been discovered. The risk factors for getting anal cancer are:

· HPV infection – Most anal cancers are related to human papillomavirus (HPV) infection. A subtype of HPV, known as HPV-16, is often associated with squamous cell carcinoma of the anal canal. This virus is also found in anal warts, and studies have proven that warts with the HPV-16 subtype are more likely to progress into tumors when compared to others.

· Lowered immunity – A weakened immune system increases the chances of infection with HPV and, in turn, might trigger the development of anal cancer.

· Smoking -The higher a person’s pack-year history of smoking, the higher risk of developing anal cancer.

· Gender and ethnicity – Anal cancer is more common in white women and black men.

· Other cancers – Patients diagnosed with cervical, vaginal, or vulvar cancer are at a higher risk.

· Sexual activity – Having multiple sexual partners and involving in receptive anal intercourse increases the risk of developing anal cancer.

Symptoms

The following signs may be seen with anal cancer or other less severe conditions like hemorrhoids:

Screening tests

The healthcare provider will perform a physical exam and then perform other screening tests to confirm anal cancer. This includes:

Ø Digital rectal examination (DRE) – It involves the examination of the anus and rectum. Usually, a doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for any signs of abnormalities.

Ø Anoscopy: In this test, a short, light tube called an anoscope is used to examine the anal canal to visualize abnormal areas.

Ø Anal ultrasound: Radiological studies like MRI scans can be used to see how deep cancer has grown into the tissues near the anus.

Ø Biopsy: In a biopsy, a small piece of the tumor cells or tissues is removed by a fine needle and observed under a microscope by a pathologist. This is done to confirm the presence of anal cancer and ascertain if it is related to an HPV infection.z

Anal Cancer Treatment

Different treatment options are available for patients. Combining two or more treatments is often recommended to improve the patient’s quality of life. The various types of treatment options for anal cancer are:

· Surgery – Surgery is not the first treatment for anal cancer but is often used as the last resort. Two types of surgical procedures, local resection, and abdominoperineal resection, are used. In local resection, the tumor and some of the healthy tissue surrounding it are cut off from the anus. Unlike this, the abdominoperineal resection involves the removal of the anus, rectum, and sigmoid colon, then sewing the end of the intestine into an external disposable bag outside the body.

· Chemotherapy – Drugs are administered to the patients to facilitate the death of the tumor cells or to stop them from dividing. A combination of chemotherapeutic drugs is usually given to shrink cancer. The commonly used ones are–

§ 5-fluorouracil + mitomycin

§ 5-fluorouracil + cisplatin

· Radiation therapy – High-powered beams such as x-rays or protons kill the cancer cells or prevent their metastasis. The two types of radiation therapy are internal radiation therapy and external radiation therapy. A radioactive substance is injected near the cancer site in internal radiation therapy. At the same time, in the latter case, a machine sends radiation toward the tumor area in the body.