Colorectal Cancer Screening Options Expanded Through Genetic Testing

colorectal cancer

colorectal cancer

The Food & Drug Administration’s (FDA) Aug. 12, 2014, approval of Cologuard, a new genetic testing tool, significantly expanded the noninvasive screening options available for colorectal cancer. Cologuard is a noninvasive screening test, co-invented by a doctor at Mayo Clinic and manufactured Exact Sciences Corporation in Madison, Wisconsin, which identifies DNA mutations and blood proteins in stool samples for the early detection of colorectal precancer and cancer.

While both abnormal DNA mutations and blood proteins can exit the body through fecal material when cancer cells are growing inside the colon, it is Cologuard’s added ability to detect DNA mutations in the stool sample that lends accuracy to the test. In research trials, Cologuard showed unprecedented effectiveness when compared to the fecal immunochemical test (FIT) test, which has been widely recognized in health care as the most accurate, noninvasive colon cancer screening standard. In a clinical trial of more than 10,000 people, Cologuard accurately detected 92 percent of colorectal cancers and 69 percent of the polyps most likely to develop into cancer. These results contrasted impressively with those of the FIT test, which detected only 74 percent of cancers and 24 percent of precancerous polyps in the trial.

The Centers for Disease Control and Prevention (CDC) recognizes colorectal cancer as not only the second-most deadly form of cancer in the United States today, but also the most treatable form of cancer, with a 90 percent 5-year-survival rate when detected early. Screening, which allows for early detection by testing for disease before symptoms become apparent, is especially important for detecting cancer in the colon because symptoms, such as abdominal pain and blood in the stool, often do not appear until the condition is far too advanced for effective treatment.

Government officials estimate that some 23 million Americans between the ages of 50 and 75 are not being screened for colon cancer as recommended, which results in 60 percent of detections occurring in later stages when treatment is less effective and more expensive. According to the Colon Cancer Alliance, these numbers indicate that more than half of colorectal-cancer-related deaths could be avoided with regular screening.

David Ahlquist, M.D., co-inventor of the Cologuard test and a gastroenterologist at Mayo Clinic, stated in an Exact Sciences news release that the Cologuard test was specificially designed for accuracy, ease of patient use, and widespread accessibility. Strong government support for this industry effort is evident in the historic collaborative partnership between the FDA and the Centers for Medicare & Medicaid Services (CMS) that brought Cologuard to market on the same day CMS proposed national Medicare coverage for the technology. The unprecedented interagency collaboration is part of a pilot program known as parallel review, which allows certain FDA and CMS procedures to run simultaneously, saving as much as six months from the beginning of a clinical trial to the initiation of Medicare coverage.

While FDA approval of the Cologuard test and simultaneous CMS proposal for Medicare coverage does not change the recommended medical practice guidelines for colorectal cancer screening, it does make genetic testing, in the form of a DNA stool test, available for physicians to offer to patients, with the implied promise that Medicare will pay for it, eventually.

Currently, physicians wishing to offer Cologuard to their patients may arrange to have the test kit sent directly to the patient’s home. The patient follows the kit directions, and returns a small stool sample to the Exact Sciences laboratory in Wisconsin, where the molecular tests are conducted. Results are made available through the prescribing physician in about two weeks.

Prior to the approval of the Cologuard genetic testing option, the primary screening tests available for colorectal cancer included non-invasive, modestly accurate, fecal occult blood tests and highly invasive, extremely effective, colonoscopies. These screening methods, while supported by the United States Preventive Services Task Force (USPSTF) guidelines and insurance coverage are often declined by patient choice due to anticipated discomfort and unpleasantness. While sigmoidoscopies may be covered by insurance, they are limited to examining the lower one-third of the colon. Other full-colon screening options, including barium-enhanced x-rays and computed tomography-enabled virtual colonoscopies, while noninvasive, require patients to be exposed to radiation and are not supported by USPSTF guidelines or Medicare insurance coverage.

With the FDA approval of Cologuard, the list of available screening options now includes genetic testing, which is noninvasive, highly effective, user-friendly, and potentially less expensive than other options. The National Institutes of Health (NIH) predicts the costs of genetic testing will continue to decline over time. Joint FDA and CMS support points toward USPSTF inclusion of genetic testing options in future practice guidelines.

The NIH predicts that the practice of medicine will become more personalized in the future through genetic testing technologies. Genetic information specific to an individual will not only help physicians detect an individual’s risk for diseases like colorectal cancer, but will allow doctors to formulate more accurate diagnoses, offer more patient-friendly treatment options, and co-create effective health maintenance strategies in partnership with the patient. Supporters of medical biotechnology assert that doctors and patients alike will continue to watch the quality of health care improve as colorectal cancer screening options and other health care advances expand through genetic testing.

By Lane Therrell

CDC (Colorectal Cancer)
CDC (What Is Colorectal Cancer Screening?)
Exact Sciences Corporation
American Cancer Society
Mayo Clinic News Network