FDA Approves Stool DNA Test for Colorectal Cancer Screening

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New test more sensitive than fecal occult blood tests but carries a higher risk of false-positives.
New test more sensitive than fecal occult blood tests but carries a higher risk of false-positives.

Cologuard®, a stool DNA test manufactured by Exact Sciences Corporation, has received approval from the U.S. Food and Drug Administration (FDA) for colorectal cancer screening.

The noninvasive test detects DNA changes associated with colorectal tumors, including KRAS mutations, aberrant NDRG4 and BMP3 methylation, and b-actin. It also detects hemoglobin in the stool.

 “This approval offers patients and physicians another option to screen for colorectal cancer,” said Alberto Gutierrez, PhD, director of the office of in vitro diagnostics and radiological health at the FDA's Center for Devices and Radiological Health. “Fecal blood testing is a well-established screening tool, and the clinical data showed that the test detected more cancers than a commonly used fecal occult test.”

Cologuard was compared with a fecal immunochemical test (FIT) in a study of 9,989 patients at average risk for colorectal cancer.1 Cologuard was more sensitive than FIT for detecting colorectal cancers (92.3% vs 73.8%, P=0.002) and for detecting advanced precancerous lesions (42.4% vs 23.8%, P<0.001).

RELATED: First Stool DNA Colorectal Cancer Screening Test OK'd by FDA

However, the Cologuard test yielded a higher rate of false-positives than FIT, which might lead to a higher rate of unnecessary colonoscopies. The specificity among subjects with nonadvanced polyps or negative findings was 86.6% for Cologuard and 94.9% for FIT (P<0.001).

“The robustly conducted research as part of this FDA approval process has proven that this noninvasive test is highly sensitive in detecting both early-stage colorectal cancer and the most advanced precancerous polyps most likely to develop into cancer," said David Ahlquist, MD, a gastroenterologist at the Mayo Clinic and co-inventor of the test." The test is designed for high accuracy, ease of patient use, and wide accessibility. We hope that it will make a difference and save many lives.”

When physicians order a Cologuard test, a kit is sent directly to the patient, who collects a stool sample and returns it by mail to Exact Sciences. After approximately 2 weeks, a positive or negative result is reported to the physician. Patients with positive results should undergo colonoscopy. No dietary restrictions or bowel preparation are required. Each test costs $599, according to Exact Sciences.

Simultaneously with the FDA approval, the Centers for Medicare and Medicaid Services (CMS) issued a proposed coverage determination for Cologuard, making it the first product to be reviewed through a joint FDA-CMS pilot program known as parallel review, which is intended to reduce the time between the FDA's approval of a device and its approval for Medicare coverage.

RELATED: Lower Colorectal Cancer Mortality with Removal of Low-Risk Adenomas

CMS proposes to cover the Cologuard test once every 3 years for Medicare beneficiaries who are age 50 to 85 years, asymptomatic for colorectal disease, and at average risk of developing colorectal cancer.

Currently, only about 60% of eligible Americans undergo periodic colonoscopy, so a highly sensitive, noninvasive alternative might improve overall rates of colorectal cancer screening.

However, a significant benefit of colonoscopy is its ability to detect adenomatous polyps and thus help prevent colorectal cancer. Cologuard is better at detecting cancers than at detecting polyps and therefore may not contribute to a significant reduction in the incidence of the disease.

Reference

  1. Imperiale TF, Ransohoff DF, Itzkowitz SH, et al. Multitarget stool DNA testing for colorectal-cancer screening. New Engl J Med. 2014;370(14):1287-1297.

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