You may have heard the story about how penicillin was discovered by accident: A Scottish researcher studying the influenza virus came back from vacation to find mold on a culture plate that actually prevented the growth of staphylococci bacteria. And this is not the only case in history of a scientist discovering one thing when they were searching for something else.
In 2013, healthcare company Illumina began offering a non-invasive prenatal test (NIPT) to pregnant women in an effort to find tiny DNA fragments in the women’s blood that might indicate chromosomal abnormalities in the fetuses they were carrying. Armed with that information, researchers could potentially detect genetic disorders such as Down syndrome.
Dr. Meredith Halks-Miller, pathologist and laboratory director of Illumina’s NIPT clinical lab at the time, noticed odd findings in some of the blood samples of the pregnant women. They didn’t show evidence of the chromosomal disorders the test was designed to find, but they indicated abnormalities that raised suspicions.
“I was pretty sure that these expectant mothers had cancer and didn’t know it,” Halks-Miller recalls. “I encouraged the clinical consulting staff to do more clinical follow-up for these patients even though they appeared to be healthy.”
Halks-Miller shared the information with Illumina’s chief medical officer at the time, Rick Klausner, a former director of the National Cancer Institute, who told her, “I don’t know of anything else that changes the genome the way you’re showing me here.”
Sure enough, 10 women with these DNA abnormalities were eventually diagnosed with cancer.
That led to the development of Galleri, a new multi-cancer early detection test from the healthcare company GRAIL, spun off from Illumina in 2016, with Klausner as a cofounder. The new test, expected to become commercially available by the summer of 2021, could potentially revolutionize cancer screening. And early cancer detection has the potential to lead to major reductions in both expense and mortality rates.
The beauty of machine learning
Up until now, in the U.S., there have been early-screening tests for only 5 types of cancer:
- PSA test for prostate cancer
- Colonoscopy for colorectal cancer
- Mammography for breast cancer
- Pap smear for cervical cancer
- Low-dose CT scan for people at high risk for lung cancer
But dozens of other cancers — ones for which no screening tests are available — are often detected only after they’ve begun to spread, making treatment more difficult.
Although the science behind the Galleri test is sophisticated, the underlying premise is straightforward. It uses a single blood test that can detect multiple types of cancers from DNA fragments found in the blood. In fact, in clinical studies, Galleri demonstrated the ability to detect more than 50 types of cancers, as defined by the American Joint Committee on Cancer Staging Manual. It can also indicate where the cancer is located in the body, which can help physicians determine the appropriate diagnostic workup.
Scientists have long known that cancer cells shed DNA fragments into the bloodstream, but until recently, they were unable to discern those signals from background noise. Galleri uses machine learning — essentially algorithms — to filter out the background noise. This use of algorithms means that the test may also improve over time, such as detecting additional types of cancer.
“As more people use the test, the data gathered will improve our ability to interpret the test for the next people,” Klausner explained. “So Galleri is probably going to be much better in the future. That’s the beauty of machine learning.”
The company’s models estimate that by adding Galleri to diagnosis by existing cancer screening tests, the test has the potential for earlier-stage detection of nearly 70% of cancers that result in death within five years, which translates to the potential to avert 39% of deaths that would otherwise be expected if not for early detection.
A path to early detection
As the company prepares for Galleri’s launch, Klausner explains the intentional balance of enthusiasm with a bit of skepticism. “The company has been set up from day one to be its own harshest critic, because we don’t want to emphasize hype over promise,” he says. “We’ve done large, rigorous clinical studies. We’ve put skeptics on our Scientific Advisory Board. But I feel very comfortable saying we’ve begun to break the back of this holy grail of cancer, which is early detection.”
To learn more about this groundbreaking test, visit www.grail.com/galleri.
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