Anal Cancer

Anal cancer is a rare disease, occurring in 1 in 600 adults nationwide. Survival rates are greatly affected by how early it’s detected. It starts in the one- to two-inch-long anal canal, which connects the anus to the rectum. It’s the end of the digestive system and the part of the body that excretes feces. Anal cancer is also called carcinoma of the anal canal.

Types & Stages

Anal cancers are often divided into two groups based on where they start: cancers of the anal canal (above the anal verge, which is where the canal connects to the outside skin) and cancers of the perianal skin (below the anal verge). It can also start in three different types of cells:  

  • The most common type is squamous cell carcinoma, a type of skin cancer. 
     
  • Adenocarcinoma of the anus is less common and starts in glandular cells that make the mucus that helps stools pass through smoothly. 
     
  • Melanoma, another rare type of anal cancer, starts in skin cells called melanocytes.

The earlier anal cancer is detected, the better the survival rates. For example, when detected in stage 1, the five-year survival rate is 70 percent. However, at stage 4, it drops to 20 percent.

Signs & Symptoms

The symptoms of the most common type of anal cancer, squamous cell carcinoma, tend to be similar to those of hemorrhoids. Because of this — and its relatively low rate of occurrence in relation to other cancers — it tends to be misdiagnosed or overlooked. See your doctor if you experience any of the following:

  • anal bleeding
  • a lump or mass at the anal opening
  • persistent itching and pain
  • drainage or discharge
  • swollen lymph glands in the groin area
  • changes in bowel habits

Anyone experiencing these symptoms should speak with their primary care physician.

Diagnosis

If your doctor suspects a problem, you should get referred to a colorectal surgeon who can run a number of tests. These include:

  • a physical exam,
  • a digital exam,
  • a palpable groin exam,
  • an anoscopy, which is an exam of the anal canal and rectum with an anoscope. An anoscope is a small-diameter plastic or metal hollow tube (slightly wider than a finger) with an insert called an obturator. The device is about 5 inches long.
  • a full colonoscopy, a procedure that lets your doctor check the inside of your entire colon (large intestine). The procedure is done using a long, flexible tube called a colonoscope. The tube has a light and a tiny camera on one end. It’s put in your rectum and moved into your colon.

At Stony Brook Cancer Center, if  we uncover any lesions, we can biopsy them. We also use CT and PET scanning for testing, as well as to evaluate if the cancer has metastasized or invaded any other structures around the anus.

Treatment

Anal cancer is usually treated with a combination of chemotherapy and radiation. Together, these two treatments enhance each other to kill cancer cells. Approximately 80 percent of patients respond to chemotherapy and/or radiation therapy.

Surgery might be used to treat anal cancer in certain situations. Operations might include:

  • Surgery for very small anal cancers. Though it's not common, some very small anal cancers are treated with surgery alone. The surgeon removes the cancer and some of the healthy tissue around it. This ensures that all the cancer cells are removed. This might be an option only if the cancer is very small and the surgery won't hurt the muscles that surround the anal canal. These muscles, called anal sphincter muscles, control bowel movements. Depending on your cancer, chemotherapy and radiation after surgery also may be recommended.
     
  • Surgery for cancer that hasn't responded to other treatments. If the cancer remains after chemotherapy and radiation—or recurs—your doctor may recommend abdominoperineal resection, also called APR. During APR the surgeon removes the anal canal, rectum and part of the colon. The surgeon then attaches the remaining part of your colon to an opening in your abdomen called a stoma. Waste leaves the body through the stoma and collects in a colostomy bag.

Causes & Risk Factors

Anal cancer occurs in both men and women, although is slightly more prevalent in women. Risk factors include:

  • Being exposed to human papillomavirus, also called HPV. HPV is a common virus that's passed through sexual contact. For most people, it causes no problems and goes away on its own. For others, it causes changes in the cells that can lead to many types of cancer, including anal cancer.
     
  • Increasing number of sexual partners. The greater your number of sexual partners, and the greater your partner's number of sexual partners, the greater your chance of acquiring HPV.
     
  • Having anal sex. People who have receptive anal sex have an increased risk of anal cancer.
     
  • Smoking cigarettes. People who smoke cigarettes have an increased risk of anal cancer.
     
  • Age. The risk increases over the age of 50.
     
  • Having a history of cancer. Those who have had cervical, vulvar or vaginal cancer have an increased risk of anal cancer.
     
  • Having a weak immune system. If the body's germ-fighting immune system is weakened by medicines or illness, there might be a higher risk of anal cancer. People with a weakened immune system include those taking medicines to control the immune system, such as after an organ transplant. Certain medical conditions, such as infection with HIV, also can weaken the immune system.

Screening

It’s important to have regular checkups that include a digital rectal exam. People who are at high risk, such as the HIV positive population, can now get anal pap smears to screen for the precancerous cells that can develop before anal cancer.

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