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FDA approves DNA stool test for colon cancer
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The FDA approved a stool-based test that uses DNA to detect colon cancer and precancerous growths.
Cologuard (Exact Sciences) uses a stool sample to identify certain mutations associated with colorectal cancer in the DNA of cells shed by advanced adenomas as stool passes through the large intestine and rectum. Patients who exhibit positive test results will be advised to receive a diagnostic colonoscopy.
Alberto Gutierrez
“This approval offers patients and physicians another option to screen for colorectal cancer,” Alberto Gutierrez, PhD, director of the office of in vitro diagnostics and radiological health at the FDA’s Center for Devices and Radiological Health said in a press release. “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.”
The FDA based its approval on the results of a that compared the safety and efficacy of Cologuard vs. the common fecal immunochemical test (FIT) in 10,023 patients.
According to study results, Cologuard detected 92% of colorectal cancers and 42% of advanced adenomas in the study population, whereas the FIT screening test detected 74% of cancers and 24% of advanced adenomas.
However, Cologuard was less accurate than FIT at correctly identifying individuals who were negative for colorectal cancer or advanced adenomas. Cologuard correctly yielded a negative screening result in 87% of cases, whereas FIT correctly yielded a negative screening result in 95% of cases.
FDA approval for Cologuard does not alter change current practice guidelines for colorectal cancer screening, as fecal DNA testing is not currently recommended as a method to screen for colorectal cancer by the US Preventive Services Task Force.
In response to this approval, CMS issued a proposed national coverage determination for Cologuard. In a joint FDA-CMS pilot program known as parallel review, the two agencies will concurrently review Cologuard to help reduce the time between the FDA’s approval of a device and Medicare coverage.
“This is the first time in history that FDA has approved a technology and CMS has proposed national coverage on the same day,” Patrick Conway, MD, chief medical officer and deputy administrator for innovation and quality for CMS, said in the release. “This parallel review represents unprecedented collaboration between the two agencies and industry and, most importantly, will provide timely access for Medicare beneficiaries to an innovative screening test to help in the early detection of colorectal cancer.”
CMS proposes to cover Cologuard testing once every 3 years for Medicare beneficiaries who meet the following criteria:
- Aged 50 to 85 years;
- Asymptomatic: no signs or symptoms of colorectal disease, including lower gastrointestinal pain, blood in stool, positive guaiac fecal occult blood test or fecal immunochemical test;
- Average risk for developing colorectal cancer: no personal history of adenomatous polyps, of colorectal cancer, or inflammatory bowel disease, including Crohn’s Disease and ulcerative colitis; no family history of colorectal cancers or an adenomatous polyp, familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer.
Perspective
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Richard M. Goldberg, MD
Expanding the options for colorectal cancer screening increases the likelihood that more people will be screened, permitting early detection of cancers. This leads to higher cure rates and removal of premalignant polyps, thus preventing cancer. By repeating the test at 3-year intervals, there is a high potential to replicate the results delivered by the serial deployment of cervical Pap smears. Serial testing can detect pathology missed by false-negative studies, and the growth and transformation of premalignant to malignant growths in the colon is a process that generally takes years and allows for repeat testing.
Undoubtedly, some patients will find submitting a stool sample preferable to submitting to colonoscopy prep, sedation and recovery — a daylong process at best. Health economists can discern the truth of the hypothesis that, by avoiding the need for screening colonoscopy and its potential for complications in a significant number of Medicare and Medicaid patients, CMS will realize cost savings.
It seems likely that Cologard can prevent cancer, permit early diagnosis and benefit the public health in a cost-efficient way. Refining the test’s utility with further studies will help us employ this novel technology to best advantage. In addition, the notion that — through years spent problem-solving — researchers have found a way to discern the genetic changes heralding cancer and polyps in those few cells exfoliated from the pathologic lesions that contain those genes that are hiding among the other detritus in stool is just plain “cool science.”
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