With the recent FDA approval of the stool DNA test Cologuard for colorectal cancer (CRC) screening, the question is, for whom is this new screening method appropriate? Cologuard is one of many colorectal screening methods, and although colonoscopy is the “gold standard” for CRC screening in the United States, many adults are still resistant to this invasive test. Cologuard is also based on fecal DNA and has been shown to be more sensitive. A pivotal clinical trial showed that Cologuard was more sensitive than fecal immunochemical testing (FIT) in detecting colorectal cancer and advanced precancerous lesions (adenomas and serrated clot-free polyps) by a ratio of 92% vs. 74% (P=0.002) and 42% vs. 24% (P<0.001), respectively. In contrast, Cologuard was less able to correctly identify patients with negative CRC or advanced lesions than FIT (87% vs. 95%, P<0.001). Cologuard is expected to enable screening of patients who avoid colorectal cancer screening because of the discomfort and time spent on colonoscopy. According to Dr. Daniel Chung of the Massachusetts General Hospital Cancer Center, "Patients who are not screened for colorectal cancer and who prefer a noninvasive test are more likely to undergo this approach." Another clinician even stated in the Journal of the American Medical Association that Cologuard may one day replace colonoscopy and sigmoidoscopy as the preferred initial screening method in the United States. However, it remains to be seen whether the new fecal DNA test will become widely available. In fact, Dr. Imperiale and colleagues conducted a Cologuard study of 10,000 patients at 90 centers, saying the available data still "do not determine which tests or methods are better or more preferred. Clinicians and patients can decide whether to choose Cologuard based on their needs, but one thing is certain: patients who test positive for Cologuard must undergo colonoscopy. Detection and Prevention of Colorectal Tumors Cologuard includes DNA tests that target various genetic mutations, such as the KRAS gene, in addition to measuring hemoglobin. As with the previous stool DNA test, Cologuard is better at detecting cancer than adenomas and non-tipped serrated polyps. That said, cologuard is better suited to detecting tumors than preventing them. "Like all noninvasive tests, Cologuard does not successfully detect colon polyps," says Dr. Chung. "It has a detection rate of only 17 percent for nonadvanced adenomatous polyps and a sensitivity of 40 percent in identifying advanced adenomas. Advanced adenomas are the most likely of all polyps to progress to invasive cancer." Colonoscopy is not the best screening method, and only about 60 percent of eligible Americans are screened for CRC. Screening for colorectal cancer remains suboptimal, and giving patients a better choice of noninvasive screening methods could help increase patient motivation to participate in CRC screening. Dr. Imperiale recommends Cologuard screening every 3 years. He believes that the dual advantages of interval and noninvasiveness of Cologuard compared to sigmoidoscopy every 5 years and annual fecal occult blood testing contribute to its widespread use. Currently, Cologuard appears to be the best non-invasive screening method. It has a better detection rate than FIT for advanced adenomas and advanced serrated polyps. Moreover, previous fecal DNA tests had average sensitivity for colorectal cancer and even lower sensitivity for advanced adenomas. Practicality and Cost of Cologuard To order a test kit, physicians must first register on the Cologuard website, and then a company representative will contact them to complete the process. After the physician places the order, the kit will be mailed directly to the patient. Each kit includes a bag and prepaid box for the patient to send a stool sample to Exact Science Laboratories in Wisconsin. It takes more than 2 weeks for Cologuard results to be returned to the physician. Results are reported as "negative" or "positive" only. A positive result may indicate the presence of cancer or advanced adenoma and should be followed by a colonoscopy. The test is not suitable for everyone. In this clinical trial, researchers excluded adult patients with a history of GI tract tumors or inflammatory bowel disease and patients with a personal or family history of colorectal cancer.