Cologuard: The Stool DNA-Based Approach

Cologuard is a first-of-its-kind, noninvasive colon cancer screening test that patients can use at home. Once Cologuard is prescribed and ordered by a doctor, the test is shipped to the patient. No bowel preparation is required, and there are no dietary restrictions. In a 10,000-patient clinical study, Cologuard found 92% of colon cancers.1 It also found 69% of high-risk precancers (high-grade dysplasia), those most likely to develop into cancer.

Every day, millions of normal cells are shed from the colon wall into the stool stream. As these cells degenerate, they release DNA. All colon cancers start as polyps, and as those polyps develop, they also shed cells into the stool stream. Some of these cells contain altered DNA, reflecting acquired mutations found in precancerous adenomas and cancer.

With Cologuard, the Exact Sciences Stool DNA-Based Colorectal Cancer Screening Test, a patient collects a stool sample at home and mails it to Exact Sciences Laboratories using a prepaid and pre-addressed return label provided with the kit. The lab processes the sample through a series of sophisticated laboratory procedures to isolate specific DNA targets. The targeted DNA is then amplified and analyzed for molecular alterations associated with cancerous and precancerous conditions of the colon and rectum.

Cologuard is intended for the qualitative detection of colorectal neoplasia associated DNA markers and for the presence of occult hemoglobin in human stool. A positive result may indicate the presence of colorectal cancer or advanced adenoma and should be followed by a diagnostic colonoscopy. Cologuard is indicated to screen men and women 50 years or older, who are at typical average-risk for colorectal cancer. Cologuard is not a replacement for diagnostic colonoscopy or surveillance colonoscopy in high risk individuals. Cologuard is available by prescription only.

Both false positives and false negatives do occur. In the clinical study of Cologuard, 13% of people without cancer or precancer tested positive. Any positive result should be followed by a diagnostic colonoscopy. Following a negative result, patients should continue participating in a screening program at an interval and with a method appropriate for the individual patient. Cologuard performance when used for repeat testing has not been evaluated or established.

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  1. Imperiale TF, Ransohoff DF, Itzkowitz SH, et al. Multitarget stool DNA testing for colorectal-cancer screening. N Engl J Med. 2014;370(4):1987-97.