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Sunday, May 29, 2016

Noninvasive colon cancer test found 92 percent successful

A pair of newly published research studies is shedding light on efforts to improve the prevention of colon cancer and colon cancer deaths.

One company-funded study at Indiana University found that a noninvasive colon cancer screening test awaiting approval for sale by the U.S. Food and Drug Administration is able to detect 92.3 percent of malignant colon lesions and precancerous growths inside the large intestine.

The other study, conducted at the University of Utah, found that what is considered the gold standard of colon cancer screening tests, colonoscopies, misses about 6 percent of cancers of the large intestine and rectum.

The Indiana University study, published online and in the April 3 print edition of the New England Journal of Medicine, looked at the colon cancer screening test known as multi-target stool DNA analysis. The test not only detects traces of blood in stool samples, a colon cancer warning sign, but also uncovers genetic mutations associated with colon cancer. The study found that the current standard noninvasive stool screening tool, the fecal immunochemical test, had a 73.8 percent success rate in detecting colon cancer.

FIT, which uses antibodies to detect the presence of a protein found in hemoglobin in red blood cells, has mostly replaced older tests that look for occult, or hidden, blood in stool samples. FIT, in general, makes it easier for the person being tested to collect stool samples than other stool screening tests.

The study found that what stage a colon growth was in or where at was within the large intestine had no satistically significant impact on the multi-target stool DNA test’s ability to detect cancer.

In addition, the study found that the multi-target stool DNA test was able to detect nearly 70 percent of benign colon polyps that are in the most danger of turning cancerous, compared to roughly 45 percent for FIT.

The IU study was funded by Madison, Wisc.-based Exact Sciences Corp., which makes the multi-target stool DNA test. Nevertheless, Imperiale stressed that the results of the study don’t decide which test is “best” when multi-target stool DNA and FIT are compared.

“There are tradeoffs with each screening test,” Imperiale said. “Physician and patient should decide together which test works best for the patient based on a variety of factors.”

Although multi-target stool DNA test had a higher colon cancer detection rate, it also produces more false-positives than FIT, the IU study found. “All screening tests for low-prevalence conditions such as cancers, which include mammography for breast cancer, Pap smears for cervical cancer, and PSA tests for prostate cancer, will have more false-positive test results than true-positive test results,” said Imperiale.

In addition to the IU School of Medicine, the Regenstrief Institute Inc., the IU Simon Cancer Center, the Roudebush VA Medical Center in Indianapolis and Exact Sciences, study participants came from the University of North Carolina at Chapel Hill, the Icahn School of Medicine at Mount Sinai, Kaiser Permanente Medical Center, Boston Biostatistics Research Foundation and the Mayo Clinic.

Meanwhile, the study from the University of Utah’s Huntsman Cancer Institute that found the 6 percent colonoscopy cancer miss rate concluded the patients in whom cancers are most likely to be overlooked are 65 or older, have a family history of colorectal cancer and had previously been found to have colon polyps.

The Utah study, led by gastroenterologist N. Jewel Samadder and published online in the journal Gastroenterology, concluded factors such as the doctor failing to examine the entire colon or the patient not completing the pre-examination colon-cleansing procedure did not play a role in the missed colon cancers.

Samadder and his colleagues believe some of the “missed” colon cancers only developed to a visible state after a colonoscopy.

Samadder’s team is now undertaking an analysis funded by the American College of Gastroenterology of tissue from colon cancers missed during colonoscopies. They are trying to find genetic differences between cancers that were missed and those that were detected.

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