A biotech firm based in California has announced progress toward a blood test that can detect cancer in its early stages, at the recent American Association for Cancer Research meeting. The company, GRAIL, used full-genome sequencing to identify DNA from dying cancer cells in the blood, according to Science magazine. They were ultimately able to find cancer in 65 percent of patients that had already been diagnosed, a success rate along similar lines of other recent research into cancer blood tests.
GRAIL is one of a handful of projects working toward such a blood test, but has attracted particularly widespread attention and investment totaling over one billion dollars. It boasts some big names from the world of science on its advisory board, and is unique in its plan to use expensive full-genome sequencing that looks at all of the human genome’s 3 billion base pairs.
First, GRAIL is cataloguing mutations in the blood of patients with cancer and individuals without the disease. So far, over 10,000 individuals have enrolled in the study, with a goal of 15,000 by the end of 2018.
At the recent meeting, the company’s R & D chief Alex Aravanis discussed “early insights” from the Circulating Cell-free Genome Atlas Study.
Using samples from 878 patients with recent cancer diagnoses, and from 580 cancer-free individuals, the company employed three different tests. One looked for mutations in 500 genes with known links to cancer, a second test detected abnormal amounts of copies of genes, and a third looked for methylation patterns – chemical tags responsible for activating genes. The analysis also took into account mutations that occur in the white blood cells of aging, healthy individuals, ruling them out in order to focus specifically on cancer mutations.
The best results came from the methylation test, which successfully detected cancer in 65 percent of individuals with highly lethal cancers that are hard to detect in early stages, including pancreatic, lung, ovarian, liver, and esophageal cancers.
For metastatic cancers, which involve larger tumors, sometimes in multiple organs, and release more DNA into the bloodstream, the detection rate reached as high as 95 percent.
The rate of false positive results was also very low.
The detection rates will need to be confirmed in another set of individuals, but suggest that blood tests with detection rates around 65 percent may be within reach. The success rate is very similar to another recent study from Johns Hopkins University, which analyzed a smaller set of genes and paired those results with tests examining proteins in the blood that have been linked to cancer.
According to Luis Diaz, an oncologist with Memorial Sloan Kettering Cancer Center and a co-author of the Johns Hopkins research, a success rate of more than 65 to 70 percent may not be possible, since smaller tumors release very little DNA into the bloodstream.