Grail’s Blood Test Shows Promise but Faces Debate After Large Cancer Screening Trial
Grail, a US company founded in 2015 by genetic sequencing leader Illumina, developed a blood test designed to detect dozens of cancer types early. In 2020, it launched a large clinical trial in partnership with the UK’s National Health Service (NHS), involving about 143,000 asymptomatic participants aged 50 to 77 who underwent annual blood tests over three years. Half received the Grail test, and half a placebo. The trial aimed to increase detection of cancers at early stages 1 and 2 by 75% by 2028, reducing late-stage diagnoses (stages 3 and 4).
Results published in early 2023 showed the test did not meet its primary endpoint but did shift some diagnoses from stage 4 to stage 3 and increased early-stage detection by 16%. Grail’s Chief Scientific Officer and President, Sir Harpal Kumar, a former CEO of Cancer Research UK, emphasized the clinical significance of detecting cancers earlier, citing survival rate improvements from stage 4 to stage 3 in common cancers like colorectal and prostate. He acknowledged limitations in detecting highly lethal cancers such as pancreatic cancer but argued that earlier detection could stimulate better treatments and create a positive feedback loop.
The test’s accuracy is high with few false positives, but it misses about 50% of cancers, meaning a negative result does not guarantee absence of disease. The technology relies on advanced genetic sequencing focusing on epigenetic markers, specifically DNA methylation patterns, to distinguish cancerous signals from normal variations. Grail has performed about one million tests to refine its machine learning algorithms.
While the NHS currently does not plan to adopt the test into routine screening, some experts see value in the earlier-stage detection it offers. Google Health’s AI architect Alex Brodetsky highlighted that improving signal processing could enhance the test’s performance. Grail’s test is commercially available in the US, Canada, and Israel, priced at $950 in the US and 4,000-5,000 shekels in Israel, mostly paid out-of-pocket as private insurers rarely cover it. FDA approval is pending, expected next year.
Grail faces competition from companies like Guardant and Exact Sciences, with similar multi-cancer early detection tests in development. Kumar envisions the test becoming a routine part of healthcare to reduce severe cancer cases and improve treatment outcomes, though he stresses that cancer risk also involves chance and that early detection remains crucial. The test’s epigenetic approach may also have future applications beyond cancer, potentially transforming disease diagnosis and management.
