Colon Cancer

Colorectal cancer is the third most common cancer in the United States and the third leading cause of cancer-related deaths.1 Less than 1% of these cases are related to inflammatory bowel disease.2 However, if you have inflammatory bowel disease, your risk of colon cancer increases.

One study showed that the risk of colon cancer was 2.6 times higher for people with Crohn’s disease.3 Among people with Crohn’s disease, 5 cases of colon cancer are diagnosed for every 10,000 patient years. The risk of colon cancer in people with ulcerative colitis is about the same.2

Which people with Crohn’s disease are at the most risk of colon cancer?

Certain features of Crohn’s disease increase the risk of colon cancer.

Disease location. Pre-cancerous cells only appear in areas of inflammation.4 Therefore, the risk of colon cancer is highest for people who have Crohn’s colitis, which is a type of Crohn’s disease that affects the colon. In one study, the risk of colon cancer was 13 times higher for people with this type of Crohn’s disease.3 With ileocolitis, the risk of colon cancer is increased about 4.6 times. Ileocolitis affects the small intestine and colon. If the small intestine is the only part of the digestive tract affected by Crohn’s disease, a person is not at higher risk of colon cancer.

Age at diagnosis. Patients diagnosed with Crohn’s disease before age 30 years are at greater risk of developing colon cancer.3 This is because the risk of colon cancer increases for every 10 years a person has Crohn’s disease.

Disease extent and complexity. The more of your digestive tract that is affected, the higher the risk of colon cancer.3 There is also some evidence that complications such as perianal fistula and strictures puts a person at higher risk of colon cancer.2

Which people with ulcerative colitis are at the most risk of colon cancer?

Certain characteristics of ulcerative colitis increase the risk of colon cancer.

The duration of disease. The risk of colon cancer increases with the length of time there is inflammation in the colon, with some studies finding that the risk of colon cancer increases exponentially in people who have had ulcerative colitis for over 30 years.5

The extent of ulcerative colitis. The more of the large intestine that is affected, the higher the risk of colon cancer. In one trial that followed more than 3,000 people with ulcerative colitis, the risk of colon cancer was 1.7-fold for people with proctitis, 2.8-fold in people with left-sided colitis, and 14.8-fold in people with pancolitis, compared to the general population.5

Age at diagnosis. Some studies have found that children who are diagnosed with ulcerative colitis before age 15 may be at a higher risk of developing colon cancer. However, other studies have not confirmed these findings.5

Besides inflammatory bowel disease, what are other risk factors for colon cancer?

Having Crohn’s disease or ulcerative colitis are risk factors for colon cancer. Other factors that increase your risk are:6

  • Being older than 50 years.
  • Having polyps in your colon or rectum.
  • Having ovarian, endometrial, breast, or previous colon cancer.
  • Having a first-degree relative with colorectal cancer, especially if that person was diagnosed before age 50.2 First-degree relatives are a parent, sibling, or child.
  • Having certain inherited disorders: familial adenomatous polyposis or hereditary nonpolyposis colon cancer (Lynch Syndrome).

People with both ulcerative colitis and a liver disease called “primary sclerosing cholangitis” have a higher risk of colorectal cancer.2 Some studies have shown this also is true for patients with Crohn’s disease and primary sclerosing cholangitis,7 while others have shown no link.8

What are symptoms of colon cancer?

Ideally, signs of colon cancer are found through screening before you have any symptoms.6 It is easier to treat colon cancer if it is found early. In some cases, you might even be able to prevent pre-cancerous growths from turning into cancer.9

Colon cancer causes similar symptoms as inflammatory bowel disease. For example, both can cause changes in bowel habits, such as diarrhea or constipation. You may feel the need to have a bowel movement that is not relieved by doing so. Other symptoms include rectal bleeding, abdominal pain and cramping, weight loss, and fatigue.

What tests are used to screen for colorectal cancer?

In a general population, the recommendation is to begin screening for colorectal cancer after age 50. Three main tests are used to screen for colorectal cancer in the general population (Table 1).10

Table 1. General Population: Screening Tests for Colorectal Cancer

Screening Test Testing Frequency in a General Population
Fecal occult blood test Every year
Sigmoidoscopy Every 5 years
Colonoscopy Every 10 years

Source: Centers for Disease Control and Prevention. Colorectal cancer screening guidelines.

Screening recommendations are different for people with inflammatory bowel disease, because of the greater risk of colon cancer. The Crohn’s and Colitis Foundation’s recommendations for people with inflammatory bowel disease are in Table 2.11 Recommendations from other organizations such as the American Cancer Society or the American Gastroenterologic Association are similar.4,12

Table 2. Inflammatory Bowel Disease: Recommendations for Colorectal Cancer Screening

Question Crohn’s Disease Ulcerative Colitis
Do I need additional screening and surveillance? You should have additional screening and surveillance (repeat testing) if Crohn’s disease affects more than one-third of your colon. People with ulcerative colitis should be screened for colorectal cancer.

Regular surveillance (repeat testing) is recommended for people with extensive colitis, left-sided colitis, primary sclerosing cholangitis, or other risk factors. People with proctosigmoiditis are not at greater risk of colorectal cancer than the general population and should follow standard colorectal prevention recommendations.

When should screening start? About 8 to 10 years from first inflammatory bowel disease symptoms.
What screening test should be done? Colonoscopy with multiple biopsies. A variation is chromoendoscopy, a procedure that uses dyes to help the doctor to see changes in the tissue during colonoscopy. If your doctor has experience with chromoendoscopy, this procedure is recommended.
How often should the test be repeated? A surveillance colonoscopy should be done within 1 to 2 years of the screening colonoscopy. If there are no signs of pre-cancerous cells, screening should be repeated every 1 to 3 years. After you have had Crohn’s colitis for 20 years, you should have a screening colonoscopy every 1-2 years. For patients with
extensive colitis or left-sided colitis:
A surveillance colonoscopy should be done within 1 to 2 years of the screening colonoscopy. If there are no signs of pre-cancerous
cells, screening should be repeated every 1 to 3 years. After you have had ulcerative colitis for 20 years, you should have a screening colonoscopy every 1-2 years.

For patients with primary sclerosing cholangitis:
A surveillance colonoscopy should be done each year.

When is the best time for a screening colonoscopy? It is best to do the screening colonoscopy during a period of recovery (remission), if possible.

Source: Itzkowitz SH, et al. Inflamm Bowel Dis. 2005;11:314-321.

There have not been any high quality studies of surveillance colonoscopy for patients with Crohn’s disease. Therefore, no one knows for certain whether more frequent screening saves lives. However, a number of lower quality studies suggest that it is helpful.4

Can colon cancer be prevented?

Abnormal cells form polyps in the colon. Polyps can grow into cancer, but it takes many years. Polyps show up on screening tests for colon cancer. If you have a polyp, it can be removed before it becomes cancerous.9

Some of the anti-inflammatory medications that are used to treat ulcerative colitis and Crohn’s disease may reduce the risk of colorectal cancer.4 For example, some studies of mesalamine have shown that this drug is linked to a reduction in colorectal cancer.

How is colorectal cancer treated?

Colon cancer is treated with:13

  • Surgery
  • Radiation
  • Chemotherapy
  • Targeted drug therapy
  • Immunotherapy
Written by: Sarah O'Brien and Emily Downward | Last Reviewed: January 2018.
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