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New Screening Test Shows High Sensitivity in Detecting Colorectal Cancer

But precancerous sensitivity is low, disappointing investors (Apr. 18)

In a preliminary analysis, the Cologuard colorectal cancer screening test (Exact Sciences Corp.) met or exceeded all primary and secondary endpoints of its recently completed DeeP-C pivotal clinical trial. The new study evaluated the test’s use for the detection of colorectal cancer and precancerous polyps.

The Cologuard test demonstrated 92% sensitivity for the detection of colorectal cancer and a specificity of 87%. However, the test’s sensitivity for the detection of precancerous polyps was only 42%.

According to a report from Reuters, the test’s precancerous sensitivity — the key metric watched by investors — was well below expectations, causing shares in Exact Sciences Corp., the test’s developer, to drop by 28%.

The pivotal DeeP-C trial included 10,000 patients aged 50 to 84 years who were at average risk for colorectal cancer. The study compared the performance of the Cologuard test with that of colonoscopy and fecal immunochemical testing (FIT).

Each result from the Cologuard screening test was compared with the patient’s colonoscopy result and with the histopathologic diagnosis of any lesions that were discovered during colonoscopy. The study population included 64 cancer patients and 752 patients with precancerous polyps.

The Cologuard test is designed to detect specific changes in a patient's DNA that appear in the stool and that often indicate the presence of colorectal cancer or of the precancerous polyps most likely to develop into cancer. The test also identifies the presence of blood in the stool — another indicator of possible colorectal cancer. The latest American Cancer Society colorectal cancer screening guidelines include stool-based DNA testing as a recommended screening option.

Sources: Exact Sciences Corp.; April 18, 2013; and Reuters; April 18, 2013.

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