Pathway Genomics' direct-to-consumer cancer diagnostic earns FDA's ire

The FDA sent Pathway Genomics a letter asking the company for additional proof that its unapproved and unlisted CancerIntercept Detect blood test can detect various cancers. The "cancer stethoscope" is the only liquid biopsy that's sold directly to consumers.

The agency says it has not found any published evidence that the diagnostic, or a similar test, has been validated to screen high-risk subjects for early-stage cancer. After a consumer draws blood using a Pathway Genomics testing kit with the assistance of a phlebotomist, it is shipped backed to the company laboratory for analysis, and results (positive or negative) are available within two to three weeks.

Pathway Genomics posted a white paper on its website about the analysis of 96 "hotspot mutations," but the FDA was unimpressed, writing, "It is unclear how the literature that you cited, addressing the presence of circulating tumor DNA (ctDNA) in already-diagnosed patients, is adequate to support the expansive claims of screening for early cancer detection using ctDNA in undiagnosed patients for up to 10 different cancers with the CancerIntercept Detect."

"Based on our review of your promotional materials and the research publication cited above, we believe you are offering a high-risk test that has not received adequate clinical validation and may harm the public health," the letter continues.

In particular, the agency wants to know how the company determined the CancerIntercept's sensitivity and specificity, or the rate of false positives and false negative diagnoses produced by the test.

CancerIntercept can be purchased for a $499 annual subscription, or $699 one-time fee. (The mechanics of "subscribing" to a diagnostic test are not explained on the website.)

Various publications have been critical of the CancerIntercept. The Verge points out that the test validation described in the white paper came from patients who were known to have cancer. In other words, the white paper does not prove that test can detect mutations in those who have not yet been diagnosed with cancer.

And Dr. J. Leonard Litchfield writes on (associated with MedPage Today) that the test could cause many false positives, leading to unnecessary anxiety and expenditure.

This isn't the first time the FDA has cracked down on a direct-to-consumer diagnostic. Its most famous enforcement action was launched against 23andMe's unapproved Personal Genome Service, which could apparently tell consumers their risk of obtaining several diseases based on a sample of saliva. The test was eventually yanked from the market. And Pathway Genomics received a warning letter in 2010 for its direct-to-consumer FDA unapproved saliva collection kit.

"We assure (you) that there is physician involvement in the ordering, review and follow-up of CancerIntercept testing. We believe that CancerIntercept Detect is a laboratory developed test and, as a CLIA and CAP certified clinical laboratory, we are offering it as such. While Pathway Genomics is involved in educating and marketing the tests to physicians and consumers, we do not believe this is a direct-to-consumer model," the company wrote on its website in response to the warning letter, adding that it will respond to the FDA letter, which requested a proposed timeline for meeting with the agency within 15 business days of the Sept. 21 letter.

The FDA's doesn't currently regulate so-called laboratory-developed kits, though it has a released a plan to do so in the future. Those are regulated under the CLIA rules, which govern large diagnostic testing facilities. But the FDA pointed out that the CancerIntercept is shipped with blood collection tubes--a medical device, putting the test under its regulatory purview.

Pathway Genomics also sells the direct-to-consumer CancerIntercept Monitor for patients already diagnosed with cancer, as well as hereditary cancer tests and other diagnostics.

- read the warning letter (PDF)
- here's the company's reponse
- here's more from The Verge
- here's more from