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2010 Validation Study

Study validates Cologuard's technology,
biomarkers and clinical performance.

My name is Hongzhi Zou. I am one of the leaders of the 1,200-sample validation study of our Cologuard™ test that we conducted and reported last year. I joined Exact Sciences from the lab of Dr. David Ahlquist at Mayo Clinic. David is a well-known colorectal cancer clinician and researcher with whom Exact collaborates. The reason I joined Exact is the great potential I saw in our test, which we demonstrated through our validation study by showing its ability to detect pre-cancers before they develop into cancer. This potential to save lives is very real to all of us at Exact.

Colon cancer is among the most preventable cancers because it takes small, pre-cancerous polyps up to 15 years to progress to cancer. If we can detect those polyps and remove them, the patient never develops cancer. That's our goal and the validation study was the first chance to test our ability to reach it. It was the first major validation of the product, part of a process to evaluate and validate the test's technology, our selection of biomarkers, and the test's clinical performance in advance of our clinical trial.

The study was comprised of three subsets. The results from the 1,200 stool samples in the final two sets, which measured the test's performance, were very strong, particularly for pre-cancer detection. We achieved greater than 50 percent sensitivity for pre-cancers and 85 percent sensitivity for cancer, at 88 percent specificity. From these results, we were able to make a calculation of Cologuard's sensitivity over a series of several screenings. The performance of any screening test over regular screening intervals is what counts. Theoretically, Cologuard's cumulative pre-cancer sensitivity would be 95 percent after three screenings. Its sensitivity for cancer would be 98 percent after two screenings.

The clinical significance is clear: Cologuard has great potential as a colorectal cancer screening tool. No other non-invasive product can detect close to 50 percent of pre-cancers.

Additional analysis of our validation study data reinforced how important the test could be in the clinic. For example, the sensitivity of the test increases as the size of the pre-cancerous polyp gets bigger. Polyps of one centimeter, which are not likely to progress to cancer, were detected at a sensitivity of 64 percent. Those that have grown to greater than three centimeters were detected at a sensitivity of 91 percent. If we detect these pre-cancerous polyps with reliability that only gets stronger as they grow, we will have made another important contribution to colon cancer screening.

Our simple test has the ability to help physicians find more pre-cancerous polyps and early stage cancers, and could be used as a widely accepted adjunct to colonoscopy.

The study demonstrated the ability our Cologuard test has to achieve those goals. Our test became the first non-invasive test to detect greater than half of pre-cancers and more than 85 percent of cancer at a high level of specificity. We demonstrated that our technology is strong and our the multi-marker approach can yield significant benefits. Most important, we confirmed that Cologuard can have a significant impact on the quality of colorectal cancer screening for millions of Americans. As the company focuses on the clinical trial, we'll never lose sight of the patients our test will help.