Last updateWed, 09 Mar 2022 4am

Colorectal Cancer Screening

Jiann-Hwa Chen a, Hans Hsienhong Lin a, b

aDepartment of Gastroenterology, Buddhist Tzu Chi General Hospital, Taipei Branch, Taipei, Taiwan
bSchool of Medicine, Tzu Chi University, Hualien, Taiwan

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Colorectal cancer (CRC) was the third-leading cause of cancer death in Taiwan in 2008. The natural history of CRC provides a chance for screening and prevention. Most CRC develops from adenomatous polyps. This progression takes at least 10 years in most people. About 90% of CRC develops after 50 years of age. Screening tests can identify cancers, usually at an early stage, and polyps, which can be removed before malignant change. Removal of adenomatous polyps can reduce the risk of developing CRC by up to 90%. Several factors increase the risk of CRC: a familial history of colon adenomas, CRC, familial adenomatous polyposis, or hereditary nonpolyposis colon cancer; a personal history of treated CRC or adenoma, or ulcerative pancolitis for more than 10 years; old age; a diet high in fat and red meat and low in fiber; a sedentary lifestyle; and cigarette smoking. Colonoscopy is the best screening method, and detects most small polyps and almost all large polyps and cancers. Polyps can be removed during colonoscopy. The risk of serious bleeding or perforation is about 1/1000. In the future, computed tomography colonography may become a good screening tool. The double contrast barium enema has largely been replaced by other screening methods. Combined screening with a fecal occult blood test and sigmoidoscopy is a possible option. People with an average risk of CRC should begin screening at 50 years of age. Colonoscopy is recommended every 10 years or computed tomography colonography, sigmoidoscopy, or a double contrast barium enema every 5 years. Stool testing once per year is another alternative. Patients with an elevated risk should be screened with colonoscopy, usually beginning at 40 years of age. Screening for family members of those with familial adenomatous polyposis and hereditary nonpolyposis colon cancer should be more intense and be initiated at 20 years of age. If polyps are found and removed during a screening colonoscopy, a surveillance colonoscopy should be done 1-5 years later, according to the size and histology of the removed adenoma.


Colonoscopy; Colorectal cancer; Screening


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