FDA’s Medical Device Advisory Committee has recommended approval of the Cologuard, a home-based, noninvasive screening test for colon cancer, by an unanimous vote (10-0).
Exact Sciences, a Madison, WI-based molecular diagnostics company, conducted the largest randomized control trial in U.S. history for non-invasive screening around the Cologuard. The study, whose results are published in the New England Journal of Medicine, put the Cologuard in a head-on test against the common fecal immunochemical test (FIT) in a group of people who were at average risk for colorectal cancer.
FIT tests detect colon cancer by looking for blood in stool samples. However bleeding is not a symptom found in every patient. Cologuard, by contrast, uses DNA analysis and looks for altered DNA in stool created by cells shedded by pre-cancerous polyps in the colon.
The study, conducted at Indiana University Medical Center–Regenstrief Institute in Indianapolis, evaluated 9989 participants and found the Cologuard to be more effective in detecting colorectal cancer than the FIT – 92.3% compared with 73.8% with FIT.
The authors concluded, “In asymptomatic persons at average risk for colorectal cancer, multitarget stool DNA testing detected significantly more cancers than did FIT but had more false positive results.”
“The sensitivity of the DNA test for the detection of both colorectal cancer (92.3%) and advanced precancerous lesions (42.4%) exceeded that of FIT by an absolute difference of nearly 20 percentage points,” the study says. However the authors add that FIT was more specific than the DNA test. They attribute the higher number of false positives in the DNA test to a number of participants with benign tumors (which can read positive on a DNA test) and age-related variations.
The authors also noted, “Although our study provides some of the important values for modeling, it cannot determine which test or strategy is better or preferred.” The study concludes that, though effective, DNA testing is not ready to replace other methods and that other factors need to be examined such as the performance of alternative tests, testing intervals, complications, costs, and the ever present challenge of home-based diangostic –patient acceptance and adherence. The U.S. Preventive Services Task Force states that there is currently no screening test that is preferred over others.
News of the FDA recommendation has already sparked a good deal of public discussion having landed on the front page of Reddit, with users sharing their own cancer stories and the hope that Cologuard could help with earlier detection of colon cancer.
The FDA is not obligated to follow the committee’s recommendation as it evaluates the Cologuard for PMA approval. Materials from the FDA committee meeting, dated March 27, mention the possiblity of a post-approval study of the Cologuard.