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Tests for screening for colorectal cancer: Stool tests, radiologic imaging and endoscopy

Chyke Doubeni, MD, FRCS, MPH
Section Editors
J Thomas Lamont, MD
Joann G Elmore, MD, MPH
Deputy Editor
Judith A Melin, MA, MD, FACP


Colorectal cancer (CRC) is the second leading cause of cancer death, and accounts for approximately 9 percent of cancer deaths and 3 percent of total deaths [1]. Approximately one in three people diagnosed with CRC die of this disease in the five years after diagnosis. Removal of premalignant adenomas can prevent the cancer and removal of localized cancer may prevent CRC-related death.

Multiple test options are available for screening to detect either early-stage cancer or precancerous polyps. Test options have complementary strengths and weaknesses in the attributes of an ideal test: sensitivity and specificity, evidence of effectiveness, effect size, convenience, safety, availability, and cost. No one test is best in all these dimensions. This topic will review characteristics of the individual tests that are used for CRC screening. Screening strategies for patients with average colon cancer risk and with increased risk, as well as management of patients with colon polyps, are discussed separately. (See "Screening for colorectal cancer: Strategies in patients at average risk" and "Screening for colorectal cancer in patients with a family history of colorectal cancer" and "Familial adenomatous polyposis: Screening and management of patients and families" and "Overview of colon polyps" and "Lynch syndrome (hereditary nonpolyposis colorectal cancer): Screening and management" and "Juvenile polyposis syndrome".)


Most colorectal cancers (CRCs) arise from adenomatous polyps that progress from small to large (>1.0 cm) polyps and then to cancer. The progression from adenoma to carcinoma is believed to take at least 10 years on average [2], although this estimate is imprecise because polyps are ordinarily removed when found.

Most colorectal polyps are either adenomatous or hyperplastic. These cannot be distinguished reliably by gross appearance and therefore biopsy is required for diagnosis. Hyperplastic polyps usually do not progress to cancer.

Two-thirds of polyps are adenomas. Adenomas are more common in men than women and prevalence increases with age. In an Austrian population of 44,350 participants (average age 61 years) undergoing colonoscopy screening, adenomas were found in 25 percent of men and 15 percent of women [3]. Large adenomatous polyps (>1.0 cm) are more likely to progress to cancer than smaller ones but are less common [4]. Some colon cancers arise from non-polypoid adenomas that are flat or depressed [5-7].

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Literature review current through: Sep 2017. | This topic last updated: Jun 05, 2017.
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