Anal cancer is a cancer (malignant tumor) which arises from the anus, the distal opening of the gastrointestinal tract through which stool leaves your body. It is a distinct entity from the more common colorectal cancer.
Anal cancer is typically an anal squamous cell carcinoma that arises near the squamocolumnar junction, often linked to human papillomavirus (HPV) infection. It may be keratinizing (basaloid) or non-keratinizing (cloacogenic). Other types of anal cancer are adenocarcinoma, lymphoma,sarcoma or melanoma.
- A change in bowel habits
- Bleeding may be severe
- Bleeding from the anus or rectum
- Pain in the area of the anus
- A mass or growth (lump) in the anal canal
- Anal itching or discharge
Anal cancer forms when a genetic mutation turns normal, healthy cells into abnormal cells. Healthy cells grow and multiply at a set rate, eventually dying at a set time. Abnormal cells grow and multiply out of control, and they don't die. The accumulating abnormal cells form a mass (tumor). Cancer cells invade nearby tissues and can separate from an initial tumor to spread elsewhere in the body (metastasize).
Anal cancer is closely related to a sexually transmitted infection called human papillomavirus (HPV). Evidence of HPV is detected in the majority of anal cancers. HPV is thought to be the most common cause of anal cancers.
Following are risk factors, which leads to anal cancer:
- Human papillomavirus: Examination of squamous cell carcinoma tumor tissues from patients in Denmark and Sweden showed a high proportion of anal cancers to be positive for the types of HPV that are also associated with high risk of cervical cancer. In another study done, high-risk types of HPV, notably HPV-16, were detected in 84 percent of anal cancer specimens examined. Based on the study in Denmark and Sweden, Parkin estimated that 90% of anal cancers are attributable to HPV
- Sexual activity: Having multiple sex partners due to the increased risk of exposure to HPV. Receptive anal intercourse, whether male or female, increases the chances of anal cancer sevenfold due to HPV. Those who engage in anal intercourse with multiple partners are 17 times more likely to develop anal cancer than those who do not
- Smoking: Current smokers are several times more likely to develop anal cancer compared with nonsmokers. Epidemiologist Janet Daling, Ph.D., a member of Fred Hutchinson's Public Health Sciences Division, and her team found that smoking appears to play a significant role in anal-cancer development that is independent of other behavioral risk factors, such as sexual activity. More than half of the anal-cancer patients studied were current smokers at the time of diagnosis, as compared to a smoking rate of about 23 percent among the controls. "Current smoking is a very important promoter of the disease," said Daling. "There's a fourfold increase in risk if you're a current smoker, regardless of whether you're male or female." They explained that the mechanism behind smoking and anal-cancer development is unknown, but researchers speculate that smoking interferes with a process called apoptosis, or programmed cell death, which helps rid the body of abnormal cells that could turn cancerous. Another possibility is that smoking suppresses the immune system, which can decrease the body's ability to clear persistent infection or abnormal cells
- Immunosuppression, which is often associated with HIV infection
- Benign anal lesions
- A history of cervical, vaginal or vulval cancers
- Cloacogenic. Cloacogenic carcinoma is a rare tumor of the anorectal region originating from a persistant remnant of the cloacal membrane of the embryo. The tumor accounts for 2-3% of anorectal carcinomas and occurs more than twice as often in women
- Older age. Most cases of anal cancer occur in people age 50 and older
- Many sexual partners. Men and women who have many sexual partners over their lifetimes have a greater risk of anal cancer
- Anal sex. Men and women who engage in anal sex have an increased risk of anal cancer
- Drugs or conditions that suppress your immune system. People who take drugs to suppress their immune systems (immunosuppressive drugs), including people who have received organ transplants, may have an increased risk of anal cancer. HIV — the virus that causes AIDS — suppresses the immune system and increases the risk of anal cancer
There is no sure way to prevent anal cancer. In order to reduce your risk of anal cancer:
- Practice safer sex. Abstaining from sex or practicing safe sex may help prevent HPV and HIV, two sexually transmitted viruses that may increase your risk of anal cancer. If you choose to have anal sex, use condoms.
- Get vaccinated against HPV.Since many, if not most, anal cancers derive from HPV infections, and since the HPV vaccine before exposure to HPV prevents infection by some strains of the virus and has been shown to reduce the incidence of potentially precancerous lesions, scientists surmise that HPV vaccination may reduce the incidence of anal cancer. Two vaccines — Gardasil and Cervarix — are given to protect against HPV infection. Both boys and girls can be vaccinated against HPV. The vaccine has been used before to help prevent cervical, vulvar, and vaginal cancer, and associated lesions caused by HPV types 6, 11, 16, and 18 in women.
- Stop smoking. Smoking increases your risk of anal cancer. Don't start smoking. Stop if you currently smoke.
Tests and procedures used to diagnose anal cancer include:
- Examining your anal canal and rectum for abnormalities. During a digital rectal exam, your doctor inserts a gloved, lubricated finger into your rectum. He or she feels for anything unusual, such as growths.
- Visually inspecting your anal canal and rectum. Your doctor may use a short, lighted tube (anoscope) to inspect your anal canal and rectum for anything unusual.
- Taking sound wave pictures of your anal canal. In order to create a picture of your anal canal, your doctor inserts a probe, similar to a thick thermometer, into your anal canal and rectum. The probe emits high-energy sound waves, called ultrasound waves, which bounce off tissues and organs in your body to create a picture. Your doctor evaluates the picture to look for anything abnormal.
- Removing a sample of tissue for laboratory testing. If your doctor discovers any unusual areas, he or she may take small samples of affected tissue (biopsy) and send the samples to a laboratory for analysis. By looking at the cells under a microscope, doctors can determine if the cells are cancerous.
Anal cancer is a serious disease. But treatments are effective, and most people can be cured.
About half of all anal cancers are found early, before the cancer has spread beyond the anus. This is called localized cancer. The 5-year survival rate for localized anal cancer is 80%.
Sometimes, the cancer isn't found until it has spread to the lymph nodes or other areas around the anus. This is called locally advanced cancer. The 5-year survival rate for locally advanced anal cancer is 60%. If the cancer has spread to other parts of the body, this is called metastatic cancer. The 5-year survival rate for metastatic anal cancer is about 31%.
The overall 5-year survival rate for anal cancer is about 65%.
Combined chemotherapy and radiation:
- Chemotherapy. Chemotherapy drugs are injected into a vein or taken as pills. The chemicals travel throughout your body, killing rapidly growing cells, such as cancer cells. Unfortunately they also damage healthy cells that grow rapidly, including those in your gastrointestinal tract and in your hair follicles. This causes side effects such as nausea, vomiting and hair loss.
- Radiation therapy. Radiation therapy uses high-powered beams, such as X-rays, to kill cancer cells. During radiation therapy, you're positioned on a table and a large machine moves around you, directing radiation beams to specific areas of your body in order to target your cancer. Radiation may damage healthy tissue near where the beams are aimed. Side effects may include skin redness and sores in and around your anus, as well as hardening and shrinking of your anal canal.
- Surgery to remove early-stage anal cancers. Very small anal cancers may be removed through surgery. During this procedure, the surgeon removes the tumor and a small amount of healthy tissue that surrounds it. Because the tumors are small, early-stage cancers can sometimes be removed without damaging the anal sphincter muscles that surround the anal canal. Anal sphincter muscles control bowel movements, so doctors work to keep the muscles intact. Depending on your cancer, your doctor may also recommend chemotherapy and radiation after surgery.
- Surgery for late-stage anal cancers or anal cancers that haven't responded to other treatments. If your cancer hasn't responded to chemotherapy and radiation, or if your cancer is advanced, your doctor may recommend a more extensive operation called abdominoperineal resection, which is sometimes referred to as an AP resection. During this procedure the surgeon removes the anal canal, rectum and a portion of the colon. The surgeon then attaches the remaining portion of your colon to an opening (stoma) in your abdomen through which waste will leave your body and collect in a colostomy bag.
- Mayo Clinic