A new blood test developed by GRAIL Inc. has shown itself to be highly accurate at screening for numerous types of cancer. Trials of the test went remarkably well. The test was able to detect and even localize the point of origin of over 20 types of cancer. It did so by “detecting methylation patterns associated with cancer in free-floating DNA in blood.” This breakthrough could enable cases to be identified and treated far earlier, when it is more likely for the treatment to succeed.
The test uses next-generation sequencing technology that can probe DNA for these tiny chemical tags called methylation. The tags influence whether genes are active or inactive – they are the “methylation patterns associated with cancer.” As disease develops, changing the genes, the test can spot that.
The trials found the new test could pinpoint the cancer source close to 90% of the time, even for diseases like ovarian and pancreatic disease, which are some of the most difficult to spot. Study lead author, Dr. Geoffrey Oxnard of Boston’s Dana-Farber Cancer Institute, part of Harvard Medical School, said:
Our work indicated that methylation-based assays outperform traditional DNA-sequencing approaches to detecting multiple forms of cancer in blood samples. The results of the new study demonstrate that such assays are a feasible way of screening people for cancer.
The Study
The study involved the researchers using the test to analyze 3,583 blood samples – specifically looking at the cell-free DNA which enters the bloodstream after becoming detached when its parent cell dies. Some of the samples came from patients with cancer, some from people who had not been diagnosed with cancer at the time of the blood draw.
Of the samples, 1,530 came from patients diagnosed with cancer. The samples comprised over 20 types of cancer – including hormone receptor-negative breast, colorectal, esophageal, gallbladder, gastric, head and neck, lung, lymphoid leukemia, multiple myeloma, ovarian, and pancreatic cancer. The rest of the 2,053 samples came from people without cancer.
The Results
The results were very specific with positive results mainly delivered only when cancer was actually present. When a cancer signal was detected, the test also correctly identified the tissue of origin (the tissue where the cancer began).
- The overall specificity was 99.4%.
- Only 0.6% of the results incorrectly indicated that cancer was present.
- Out of the 76% of the high mortality cancers that were accurately detected: 32% was for patients with stage one cancer; 76% was for those with stage two; 85% was for stage three; and 93% was for stage four. Accuracy across all cancer types was 55%.
Conclusion
“Detecting even a modest percent of common cancers early could translate into many patients who may be able to receive more effective treatment if the test were in wide use,” said Oxnard. For now, only half of patients can expect to receive a diagnosis before they reach stage three or four. However, the researchers’ aim is to raise this number so that by 2028 three quarters of cancer patients are diagnosed at either stage one or two.
