If you could take a simple blood test that could detect multiple types of cancer while they’re still in an early and treatable stage, would you? For many, the answer would be a resounding yes.
Having a super-sensitive multi-cancer screening tool that could actually save lives is the “holy grail” for cancer researchers and physicians. The aptly named health care company Grail claims their Galleri test does just that. While there are about 20 multi-cancer early detection (MCED) tests currently in development, including Exact Science’s Cancerguard, Galleri is the most widely known and studied to date, according to Dr. Robert Volk, Hubert L. and Olive Stringer distinguished professor in cancer research at the University of Texas MD Anderson Cancer Center and deputy chair in the department of health services research.
Currently, only five cancers have standard screening tests: breast, colorectal, cervical, lung and prostate. The majority of cancers don’t have one, which means MCED tests have the potential to fill a major gap. “The big advantage is identifying cancers where there currently isn’t a screening modality available,” Volk tells Yahoo Life. “Many cancers are on that list.”
Galleri, for example, screens for more than 50 different types of cancer from a single blood draw, including lung, breast, colon, liver and ovarian cancer, along with leukemia and lymphoma and rare cancers doctors don’t typically screen for, such as soft tissue sarcoma.
Some say cancer tests like Galleri are already saving lives. Gilbert Milam Jr., a rapper and entrepreneur with a family history of cancer, took the Galleri test in 2021 and got back results that indicated colon cancer. A colonoscopy confirmed he was stage III, which led to surgery, radiation and chemotherapy. Milam is now free of cancer. “That test saved my life, and that’s a fact,” Milam told KFF Health News.
However, in an investigation published in the BMJ, critics say that the Galleri test may be “overhyped,” with some voicing concerns that there isn’t sufficient evidence “on whether the benefits of testing outweigh any potential harms and at reasonable cost.”
So is this blood test worth it and does it save lives? And how does it detect so many cancers? Here’s what experts want you to know.
How does the test work?
Cancers shed DNA from dying cells into the bloodstream. Blood tests like Galleri can screen for that tumor DNA before people experience any telltale symptoms. These tests, however, don’t diagnose a specific cancer. They’re more like a red flag that leads to further investigations and testing. Grail says the Galleri test can indicate where the tumor originated from with 88% accuracy thanks to DNA fragments unique to specific cancers. “That tells you where to start looking,” says Volk.
According to Grail (who did not respond to Yahoo Life’s request for comment), the vast majority — nearly 99% — of people who take the Galleri test will screen negative for cancer. For about 1% of those ages 50 to 79, test results will show a cancer signal was detected, along with the organ or tissue type associated with that specific cancer signal. An estimated 40% of these individuals will have a confirmed cancer diagnosis after a diagnostic evaluation by a health care provider.
What are the benefits and downsides of the test?
The advantage is that all of this can be done with a simple blood test long before any noticeable symptoms, says Dr. Mothaffar Rimawi, executive medical director of the Dan L. Duncan Comprehensive Cancer Center at Baylor College of Medicine. “It’s not invasive,” he tells Yahoo Life.
As with most blood tests, false-negatives can happen, meaning results could come back negative when a cancer does exist — although Grail reports that negative cancer test results from Galleri are 98.5% accurate. There’s also the risk of a false-positive, which is when the test comes back positive but the patient doesn’t have cancer. “That causes a lot of unnecessary work-up” — from expensive scans to biopsies — “and a lot of anxiety,” Rimawi says. However, Grail reports that the Galleri test has a low false-positive rate of 0.5%.
One big downside, say experts, is that there isn’t any evidence yet from long-term randomized trials that using an MCED test like Galleri will lead to a lower death rate from cancer. Volk explains that randomized controlled trials are “the gold standard” for proof, but adds that they take many years to be completed. “Those studies are absolutely needed and currently, we don’t have that,” he says, adding: “The jury is definitely out with these tests.”
Rimawi agrees. “One question we have to ask is, ‘Do we know if we detect a certain cancer, say, liver cancer, early on, are we really impacting outcomes — mortality — for these patients?” he says. “The question is, does early diagnosis lead to early intervention, which leads to a different outcome?”
How much does the test cost?
The Galleri test — which isn’t covered by insurance — doesn’t come cheap. At $949 a pop, it’s out of the price range of most people. But beyond that, there’s also the potential cost of additional testing if the blood test detects cancer.
Blood tests like these also don’t mean you can skip routine cancer screening tests like colonoscopies and mammograms. “It should be in addition,” says Volk. “They support one another.”
Rimawi says that some of his patients share how uncomfortable mammograms are, for example, and ask about alternatives. “Patients ask, ‘We need to have a mammogram-free option and can this test replace that?’ The answer is no, because we don’t have the longitudinal controlled trials that tell us that every tumor detected by a mammogram could be detected by this test,” he says. “We don’t have that data yet.”
Should you get a multi-cancer early-detection blood test?
The Galleri test, which is available by prescription from a health care provider or through independent telehealth providers, is recommended for adults with a higher risk for cancer, including those aged 50 or older.
But whether or not you should get the test depends on your disease risk, including family history — and your risk tolerance, says Rimawi. For example, if you’re from a family where everyone lives until their 80s and 90s and has no history of cancer, “do you really want to do this test and come up with a false-positive?” he says. “Versus someone whose family is riddled with cancer or even patients who have a genetic mutation that can lead to a higher risk of cancer, particularly for cancers like pancreatic cancer — it’s a very deadly cancer. It’s one we don’t have a screening for.” For patients like that, they may say, “‘I want to do the test, and if it results in a false-positive that’s fine,’” he says.
Experts recommend going in with eyes wide open and discussing the possible benefits and downsides of the test with your health care provider — and understanding that we don’t have all the answers just yet. “For this test, the evidence is still thin,” says Rimawi. “But the promise of the approach — and the technology — is exciting. I think there’s great potential for it. But we need to take it through the scientific method to test it.”
Adds Volk: “At the end of the day, people really need to have a conversation with their doctor about the potential benefits and potential harms and really be clear about the implications — and make a good decision about it.”