A New Blood Test for Cancer, But Is It Ready for Prime Time?

A blood test capable of identifying as many as 50 cancers with a single sample has seen rapid uptake in the US.

The Galleri blood test is offered by U.S. health networks, which have collaborated with the company that developed it. Veteran’s Affairs, Mercy Health, Ochsner Health, Intermountain Healthcare, Community Health Network, Knight Cancer Institute at Oregon Health & Science University, Premier, and Cleveland Clinic are some of them.

Eric Klein, MD, of Cleveland Clinic, calls the test “game-changing” because it can detect many different types of cancer at an early stage.

The current screening methods focus on detecting one type of cancer at a time. For example, mammograms are used to detect breast cancer, and colonoscopies are used to detect colorectal cancer.

A Galleri test, in contrast, examines just one sample of blood, which is then examined for particles shed into the bloodstream by all cancers, the so-called cell-free or circulating tumor DNA. It can determine if there is cancer and where it is located.

In the words of Jeff Venstrom, MD, chief medical officer of GRAIL, the company marketing the test, “this changes our entire paradigm about cancer screening.”

It is feared, however, that widespread use of the test might be premature.

Timothy Rebbeck, a cancer expert from Harvard T.H. Chan School of Public Health and the Dana-Farber Cancer Institute in Boston, encourages having a blood test for multiple cancers as it’s a very good idea and the scientific basis for this platform is sound.

in order for this test to be accurate, it must detect very early cancers. It must also lead to a path for subsequent workup (diagnosis, monitoring, treatment, etc.),” he says.

Galleri is being offered to people who are older than 50 and who have a family history of cancer, or who are at higher risk for cancer, or who have compromised immune systems. The company recommends that people interested in the test get in touch with their health care provider, who then needs to register with GRAIL and order the test.

In addition to a prescription from a health care provider, people who want the test will have to pay for it themselves, at a cost of around $950. Not only is the test not covered by medical insurance, but it has not been approved by the FDA.

The company makes it clear that the Galleri test is not a substitute for recommended cancer screenings, such as mammograms.

This is a “screening” test for people who do not have cancer, and so it is intended to be used by primary care doctors, Rebbeck says. He warns that “clinical pathways are not yet in place” for primary care providers to process the results of the test, although he says they are being developed.

The test returns one of two possible results – either “positive, cancer signal detected” or “negative, no cancer signal detected.”

According to the company, the test also predicts where the cancer sign is coming from “with high accuracy,” which helps guide the next steps to diagnosis.

If the patient’s test comes back positive, it will likely mean that the patient has to undergo multiple follow-up tests, according to Sameek Roychowdhury, MD, PhD.

Not only will they have to go through a lot of tests, but they will also go through a lot of stress and cost, and still not find anything. Every time a person undergoes a cancer test, that is not an easy day, he says.

Based on their large-scale study, the Galleri test had a false-positive rate of less than 1%. This means that only one person of roughly 200 with no cancer in the test results came back as someone with cancer when there was no cancer in them. The test’s accuracy varies based on the type and stage of cancer.

According to Rebbeck, this test is still not very accurate when it comes to detecting very early cancers, so additional work will have to be done before it really delivers on the promise of multi-cancer early detection.

Even Venstrom agrees that the test is not yet perfect, but it will keep on refining its performance. He states that new data is expected in September.

NHS, a large, longitudinal study conducted in the United Kingdom is gathering data on how the Galleri test performs clinically. Approximately 140,000 healthy people have signed up to participate in the trial.

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