How a surprising discovery led to a new cancer screening test

How a surprising discovery led to a new cancer screening test

(BPT) – 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.

One kind of research leads to new discoveries

In 2014, healthcare company Illumina was conducting a study involving blood tests from around 150,000 pregnant women, hoping to learn how to identify chromosomal abnormalities in the fetuses they were carrying from DNA fragments in the mothers’ blood. Armed with that information, researchers could potentially detect genetic disorders from Down syndrome to cystic fibrosis.

While conducting that research, however, they discovered something else – DNA abnormalities in about 10 of the blood samples that a pathologist could not interpret. A pathologist working on the test shared her findings with the company’s chief medical officer at the time, Dr. Rick Klausner, who is also a former director of the National Cancer Institute.

‘I studied the samples,’ Klausner recalled, ‘and I realized these women had cancer. I didn’t know anything else that changes the genome in that way.’

The research team followed up with the women to find that one had already been diagnosed with cancer after her blood test, and the others turned out to have cancer, as Klausner predicted, although they hadn’t yet shown symptoms and appeared healthy.

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:

  1. PSA test for prostate cancer
  2. Colonoscopy for colorectal cancer
  3. Mammography for breast cancer
  4. Pap smear for cervical cancer
  5. 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, an earlier version of 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


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