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New noninvasive test reported effective for colorectal cancer screening

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A new noninvasive screening test has been reported to detect more instances of colon cancer and potentially cancerous polyps than a currently available test. The findings were published on March 19 in the New England Journal of Medicine.

According to the Los Angeles County Department of Public Health, colorectal cancer is the second most common cause of cancer death in the county, behind lung cancer. The study authors note that the underlying process of the cells becoming malignant can be easily determined via screening methods. They explain that screening procedures are currently available to detect the disease and that these tests are cost-effective. Despite the availability of these tests, a significant substantial proportion of Americans do not undergo screening. Thus, a simple, noninvasive test with high sensitivity for both colorectal cancer and advanced precancerous lesions is likely to increase the number of individuals that undergo screening. As a result, deaths from colorectal cancer could be re reduced.

The investigators conducted a study of Cologuard, which is a multitarget stool DNA test, meaning that a patient only has to provide a stool sample for testing. The primary goal of the study was to determine the performance characteristics of Cologuard for the detection of colorectal cancer. The secondary goals were to determine the performance of the test for the detection of advanced precancerous lesions and to compare it with a commercially available fecal immunochemical test (FIT) for the detection of both colorectal cancer and advanced precancerous lesions.

The study group comprised 9,989 individuals for evaluation; 65 (0.7%) had colorectal cancer and 757 (7.6%) had advanced precancerous lesions found with colonoscopy. The investigators found that the sensitivity for detecting advanced precancerous lesions was 42.4% with Cologuard and 23.8% with FIT. The rate of detection of polyps with high-grade dysplasia (precancerous cells) was 69.2% with Cologuard and 46.2% with FIT; the rates of detection of polyps measuring 1 cm or more were 42.4% with Cologuard and 5.1% with FIT. Both tests were accurate for detecting patients with early cancers or no cancer (Cologuard: 86.6%; FIT: 96.4%). The numbers of individuals who would need to be screened to detect one cancer were 154 with colonoscopy, 166 with Cologuard, and 208 with FIT.

The authors concluded that among asymptomatic individuals with an average risk for colorectal cancer, Cologuard detected significantly more cancers than did FIT; however, it had more false positive results. (A false positive result is a positive test result in an individual who does not have colorectal cancer.)

Take home message:

This study reports that Cologuard is superior to other noninvasive tests for the detection of colorectal cancer. It is not as accurate as colonoscopy; however, if an individual has a positive result, he or she should then undergo a colonoscopy. The false positive rate is not a major issue because it would merely result in an individual undergoing a colonoscopy and finding that colorectal cancer was not present.