A Blood Test for Colon Cancer Sounds Great—But It's Short on Proof

The maker says it can find cancer early, but that’s a far cry from preventing colorectal cancer deaths

By SHARE

[Read: New Prostate Cancer Screening Guidelines Boost Shared Decision Making.] 

Those randomized, "gold standard" trials are very expensive and take years, which is why so many technologies find their way into use before any benefit is proven. For FDA approval, a test doesn't need to be subjected to those trials showing a survival benefit. EDP is seeking FDA approval for ColoMarker and "anticipates completing it within two years," and it expects European approval within about six months, says Kevin Jones. EDP's chief scientific officer. Further research may be necessary if the FDA requires it. 

But lacking a "well-designed, large-scale evaluation in a true screening population" and other assessments, this test, which "may someday prove to be a useful screening measure for colorectal cancer … requires a great deal more study," says Brooks. There isn't much else to go on beyond what EDP provided; a search of "CA11-19" in the medical literature finds three papers, none of which are related to colorectal cancer screening. Jones says the company is working to get "some publications out," and that can be expected "in the near future." 

The company's message about its place in the currently recommended screening regimen is murky. Jones says that its original request to the FDA will not be to replace other screening methods but to use the new tool "in intermediate years, in between tests." (The American Cancer Society's recommendations vary by test but say that a colonoscopy should be done every decade and sigmoidoscopy or virtual colonoscopy every five years.) Yet a company press release issued on December 14 begins by stating that "embarrassing and sometimes uncomfortable colonoscopies may soon be a thing of the past." Jones also says that in the future, the company "may well want to extend" use of the blood test beyond the "intermediate years." A current Q&A provided by EDP says ColoMarker will "enable the GI specialist to perform services on a more targeted basis." Many people can't or don't want to get a colonoscopy, and "an elevated CA11-19 level should encourage those individuals to have a colonoscopy." 

The Q&A also suggests use outside the USPSTF's and ACS's recommended starting age of 50. (The USPSTF goes on to recommend against routine screening in people ages 76 through 85, and it recommends against screening at all in those over 85.) "Although the risk of developing colon cancer increases with age, 12 percent of all colon cancer deaths occur in people under age 50. The colon cancer mortality rate in adults over age 75 is greater than 51 percent," it notes, responding to a question about the age range for screening. "ColoMarker will be marketed at a low cost, so it should be available to adults at all ages." Whether it will help them avoid dying from colon cancer is an open question. 

[Slide show: 11 Screening Tests You Should (or Shouldn't) Consider]