About seven years ago, researchers at the US DNA sequencing company Illumina started to notice something odd. A new blood test it ran on 125,000 expectant mothers looking for genetic abnormalities such as Down’s syndrome in their foetuses returned some extremely unexpected signals in 10 cases. Chillingly, it dawned on them that the abnormal DNA they were seeing wasn’t from the foetuses but was, rather, undiagnosed cancer in the mothers. Cancers of different types were later confirmed in all 10. “This was not a test developed for cancer screening,” says Alex Aravanis, then Illumina’s senior R&D director. “But it was evidence that it might be possible.”
In 2016, Illumina created Silicon Valley-based spin-off company Grail, with Aravanis as chief scientific officer. Backed by more than $1.5bn in funding, including money from Microsoft cofounder Bill Gates and Amazon founder Jeff Bezos, Grail is on a quest to detect multiple types of cancer before symptoms, via a single, simple blood test. The test looks at cell-free plasma to find fragments of so-called circulating tumour DNA (ctDNA) sloughed off by cancer cells. Detecting cancer sooner – before symptoms – means you can intervene earlier and people are less likely to die. While doctors can screen for breast, colon and lung cancer, most varieties of the disease can only be detected after symptoms appear.
To date, there is one company offering a blood test based on ctDNA for early cancer detection: Epigenomics began offering its test for colon cancer in 2016 based on detecting biochemical modification of a single gene.