Cancer blood-test launch raises eyebrows

A US startup called Pathway Genomics has launched the first commercial 'liquid biopsy' to identify cancerous mutations via a blood test.

Pathway will market directly to healthy people who have a high risk of developing cancer and claim that they can help people achieve an early cancer diagnosis – for $699 (£450).

For that money, the CancerIntercept test will look for 96 mutations in nine major cancer-driver genes whose presence could come from circulating tumour DNA, released from dying cancer cells.

'It's like a cancer stethoscope,' explains the promotional video on Pathway's website.

However, while the graphics may be flashy, the data are less eye-catching. In fact, there are none because Pathway has not yet published evidence in any peer-reviewed journals, nor is the test approved by the FDA.

Consequently, some health professionals are cautious about the test. Professor Keith Stewart, head of the Mayo Clinic's Center for Individualized Medicine, voiced his concerns to Bloomberg Business.

'It's fair to say it's a little premature,' said Professor Stewart, noting that 'there could be a significant risk for false-negatives or false-positives.'

False-positives could result in a user being given an incorrect and worrying diagnosis of cancer and seeking out unnecessary medical intervention; a false negative could result in someone being wrongly told they are cancer-free.

Dr Isaac Garcia-Murillas, an oncologist at the Institute of Cancer Research in London who has been working on a blood test that may predict breast-cancer relapse (see BioNews 817) told The Verge: 'I am very reticent to believe a privately funded personal genomics company's claims when there is no peer-reviewed data to support their tests or technical approaches.'

To calculate the validity of a new diagnostic test typically requires thousands of people, millions of dollars, and many years of study. Pathway's research has not yet reached this large scale.

The company's CEO, Jim Plante, admitted to The Verge that their test pool numbered only 'hundreds of samples' – and these were mostly from patients with advanced cancer, not undiagnosed people – and they have yet to complete a long-term study.

If validated, a reliable and affordable 'liquid biopsy' for cancer would represent a major breakthrough in biotechnology research. A noninvasive, low-cost test could also be used to screen large groups of people.

Ultimately, until Pathway publishes its data, it is impossible to evaluate the effectiveness of this particular test. Its chief medical officer, Glenn Braunstein, insists it has internal studies that 'will be submitted for peer review in the future'.