Despite billions of dollars invested, the relentless quest to develop blood-based cancer screening tests is progressing slowly. Clinical trials underway have yet to produce convincing results that could change behavior and impact patient outcomes. Exact Sciences’ Cologuard for colorectal cancer remains far and away the poster child for a successful, easy-to-use screening test--with caveats: it is stool-based, and compliance with US government guidelines falls far short of goals.
Start-ups developing blood-based tests for early detection of cancer have captured significant investor dollars and consumer attention for at least half a decade, but with one or two exceptions these are almost all still in development, and large-scale clinical trials required for mainstream adoption are still underway.
Only five cancers have FDA-approved screening tests of any kind. These first-generation liquid biopsies, while “amazing” in that they detect some cancers early for which screening alternatives do not exist, ”do not currently demonstrate the performance that clinical stakeholders expect for broad adoption." says Andrew Aijian, PhD, a partner at DeciBio, a consulting firm specializing in precision medicine. To become mainstream, any kind of screening test needs performance metrics that are exquisitely sensitive and specific, and therefore do not add undue burdens to the healthcare system or put patients at risk for unnecessary anxiety and procedures, he points out.