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NewYork-Presbyterian physicians discuss preventing and treating colorectal cancer.

 

What is colorectal cancer?

Colorectal cancer is a type of cancer that begins in the colon or rectum. Because colon cancer and rectal cancer have many features in common, they are sometimes referred to together as colorectal cancer. Colorectal cancer is the second leading cause of cancer-related death in the United States, but it doesn't have to be. Colorectal cancer is one cancer that can be detected early and is, in many cases, preventable. This is because most colorectal cancers begin as a small non-cancerous growth, called a polyp, in the colon or rectum. A particular type of polyp – called an adenomatous polyp or adenoma – can sometimes turn into cancer. Because it generally takes a non-cancerous adenomatous polyp several years to turn into cancer, regular colorectal cancer screening can be used to find and remove a polyp before cancer develops.

This is why screening – getting tested before symptoms occur – is so important.

Who Should Be Screened and When?

Those at Average Risk (do not have risk factors)

Women and men at average risk for colorectal cancer need to begin screening for colorectal cancer at age 50. American Cancer Society-Multisociety Task Force-American College of Radiology joint screening recommendations for those at average risk, include one of the seven options, categorized by tests that screen for both cancer and potentially pre-cancerous polyps or primarily for cancer:

Tests That Detect Polyps and Cancer:

• Colonoscopy every 10 years; OR
• Flexible sigmoidoscopy every 5 years; OR
• Double-contrast enema every 5 years; OR
• Computed tomographic colonography (virtual colonoscopy) every 5 years.

Tests That Detect Primarily Cancer

• Guaiac-based fecal occult blood test (FOBT) with high sensitivity for cancer every year; OR
• Fecal immunochemical test (FIT) with high sensitivity for cancer every year; OR
• Stool DNA test (interval uncertain).

People At Increased Risk (do have certain risk factors)

Women and men who have certain risk factors – such as a personal or family history of colorectal polyps or colorectal cancer or a personal history of inflammatory bowel disease – need to talk with their doctor about getting screened at an earlier age and with greater frequency.

Comparing Screening Tests

Colonoscopy

A colonoscopy is the most comprehensive screening test available, and the only test that allows both the detection and removal of any polyp or early cancer that is found. This screening test requires preparation with a clear liquid diet and oral laxative agent the day before, to cleanse the colon and rectum. The procedure itself involves the placement of colonoscope – a long, thin tube complete with tiny camera and light source – through the rectum and throughout the entire colon. The camera in the colonoscope transmits a video image of the lining of the colon and rectum to a television screen, which the doctor observes for polyps, cancer, or other abnormality. If the doctor sees any polyps or early cancer, he or she can use the colonoscope to remove the abnormal tissue during that same procedure. The tissue will then be sent to a laboratory to examine for cancer cells. People having a colonoscopy first undergo sedation – using a medication to make them sleepy – to minimize any discomfort. Complications with colonoscopy are very rare, but may include perforation of the colon, bleeding, or a reaction to the sedative medication. A colonoscopy should be performed by a gastroenterologist or surgeon who is specially trained in this procedure.

Flexible sigmoidoscopy

The flexible sigmoidoscopy is a screening test used to find colorectal cancer and polyps in the rectum and lower part of the colon; to pinpoint the cause of diarrhea or rectal bleeding; or to diagnose certain types of inflammatory bowel disease. Before you undergo this test, you must take a bowel prep regimen to cleanse the lower colon and rectum. Your doctor will prescribe this bowel prep regimen for you, but it usually consists of one or two enemas a few hours before the test. The test itself involves placement of a long, flexible tube – complete with camera and light source – through the rectum and throughout the lower portion of the colon. No sedation is used during this procedure. A flexible sigmoidoscopy is effective in detecting polyps and early cancers in these areas. However, a flexible sigmoidoscopy does not allow for the detection of polyps or cancers in the upper or right side of the colon. A flexible sigmoidoscopy is performed by a primary care physician or gastroenterologist. Complications with this procedure are exceedingly rare, and may include bowel perforation and bleeding.

Double-contrast barium enema

The double-contrast barium enema is one of the oldest tests used to evaluate the colon and rectum. The day before this test, you will need to follow a clear-liquid diet, and take a laxative to clear out your intestinal tract. This prep is not quite as powerful as the prep given before a colonoscopy. Just before the test, you will need to have a cleansing enema. As part of double-contrast barium enema itself, you will undergo another enema, using a tube that contains barium. The barium coats your lower digestive tract and, using an x-ray machine, allows the imaging of a clear silhouette of the colon's shape and condition. This x-ray image allows the viewing of large polyps or cancers. However, if any abnormalities are detected, a follow-up colonoscopy is needed to biopsy or remove the tissue. In an article in the New England Journal of Medicine, barium enema was found to be inferior to a colonoscopy for detecting polyps and growths. This test is performed by a radiologist, and is virtually risk-free, although it can aggravate ulcerative colitis or irritate the lining of your colon.

Computed tomographic colonography

The CT colonography, also called virtual colonoscopy, is a new technique for colorectal cancer screening. With this procedure, a device is inserted at the opening of the rectum, where a large balloon is inflated to fill the area with air so that the colon and rectum can be viewed with a CT scanner. Special computer software transforms the CT scan into a three-dimensional view of the colon and rectum. No tube is threaded through your colon, making the CT colonography less invasive than a colonoscopy, with little risk of bowel injury or bleeding. The same bowel prep required for a colonoscopy is also needed for a CT colonography. If a polyp or cancer is found during the CT colonography, a follow-up colonoscopy is needed to remove or to biopsy the abnormal tissue.

Fecal occult blood test and Fecal immunochemical test

A fecal occult blood test (FOBT), or guaiac FOBT, is performed annually and has been shown to reduce the death rate from colorectal cancer by 33%. The FOBT is a take-home test involving the placement of three stool samples on a card that is then sent to a laboratory for testing. Before an FOBT test, you must avoid red meat, citrus fruit, radishes, vitamin C supplements, aspirin, iron, and other substances known to sway the results of the test. You will need to read the test instructions carefully, noting foods, medications, and supplements that you should avoid. The FOBT works by detecting the presence of microscopic blood in the stool. This is because colorectal cancers can sometimes cause a small amount of bleeding that cannot be detected visually. However, other conditions can also cause such bleeding. If the test results show blood in the stool, a colonoscopy is needed to identify and treat the source of the bleeding. The FOBT test is done in the privacy of your own home, and is easy, painless, and inexpensive. The fecal immunochemical test (FIT) also must be performed annually and acts to detect microscopic blood in the stool. Unlike the FOBT, the FIT does not require any dietary restrictions before the test. If the test results show blood in the stool, a colonoscopy is needed to identify and treat the source of the bleeding. Like the FOBT test, the FIT is done in the privacy of your own home, is easy, and is painless.

Both of these stool tests must be performed every year to be effective. In addition, they must be performed as a take-home, multiple-sample test. A stool test done with one sample, or done during a rectal examination at the doctor's office, is NOT effective as a screening test for colorectal cancer.

Stool DNA test

Another type of screening test is the stool DNA test. This test involves the use of a stool sample to evaluate for the presence of DNA related to colorectal cancer. If the results of this test are abnormal, a follow-up colonoscopy is needed. Like the FOBT and FIT, this test is done in the privacy of your own home, is easy, and is painless.

What are risk factors for colorectal cancer?

Being over 50, having other forms of cancer or digestive diseases such as inflammatory bowel disease (IBD), Crohn's disease, or ulcerative colitis, or being from a certain genetic background such as Ashkenazi may increase one's risk of developing colorectal cancer. Influencing these factors may be difficult. But there is good news. The other risk factors for colorectal cancer are generally within your control: do not smoke; avoid heavy alcohol use; engage in regular exercise; eat a diet rich in fresh fruit, vegetables, whole grains, calcium, and vitamin D; consume little animal fats; and stay trim (avoid excess body fat).

What are its symptoms?

Colorectal cancer can have no symptoms. If you do experience symptoms, they may include a change in bowel habits, such as constipation, diarrhea, frequency of bowel movements, or narrowing of the stool that continues for more than a few days; rectal bleeding or traces of blood in the stool; stomach pain, cramping, or stomach discomfort; fatigue and weakness; decreased appetite and weight loss; jaundice (yellow-colored skin or eyes); enlarged abdomen; or feeling of discomfort in the pelvic area.

Remember that these symptoms can also be the signs of other health issues, and that only a clinician can accurately diagnose colorectal cancer. Also, please remember that screenings are important because colorectal cancer can have no symptoms and, in all cases – symptoms or not – early detection and treatment increases your chances of survival.