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Headline Hype: One simple blood test to detect 50 cancers?  Not yet

November 16, 2021

Headline Hype: One simple blood test to detect 50 cancers? Not yet

by Piri Welcsh, PhD

A new blood test is being promoted by the company that developed it and the media as a simple test that can detect 50 different cancers at the earliest stages.

For years, researchers have tried to develop a “liquid biopsy”—a simple blood test that could detect cancer earlier than current methods of screening. Ideally, a liquid biopsy would reduce the need for other types of biopsies and invasive screening procedures to identify the type of cancer and indicate how best to treat it. This type of test would be particularly helpful for small or hard-to-reach and inaccessible tumors, where surgery may be risky, painful or unable to collect enough cancer cells. Many laboratories are actively researching ways to develop these tests.

Not ready for prime time

The test currently making headlines is Galleri, which was developed by the ambitiously named company Grail. Galleri is being marketed as a way to detect over 50 types of cancer in the earliest stages when they are more treatable. While promising, the test is not yet proven to live up to its media headlines and hype. While “Grail” aptly describes the hope and need for a single accurate test for multiple cancers, the media appears to be fixated more on the company’s name than the lack of scientific basis for its claims.

  • One study showed that Galleri detected 39% of stage I, 69% of stage II, 83% of stage III and 92% of stage IV cancers.  While the test more accurately detected cancers of increasing stage, it failed to detect almost 60% of stage I cancers.
  • In another study published by GRAIL to validate Galleri, the test detected 51.5% of cancers.  Again, the sensitivity of the test increased with the stage of cancer. Galleri identified about 77% of stage III and 90% of stage IV cancers. Once again, however, the test failed to dependably detect early-stage cancers, finding only about 17% of stage I cancers and 40% of stage II cancers.
  • Early results of yet another study have also been reported by GRAIL. The PATHFINDER study looked at people older than 50 who had an elevated risk for cancer because they were smokers, previously had cancer or had an inherited mutation that significantly increased their cancer risk. In this study, the frequency of false-positive results produced by Galleri was an issue; almost 30% of the positive tests were false positives (the tests were positive for cancer when the individuals had no cancer). False-positive results can lead to additional tests, anxiety and potentially surgical biopsies.

Although the science is promising, many experts caution that liquid biopsies remain unproven, and it is unclear how well these tests perform in people who are at high risk for cancer. During the closing panel of our Annual Joining FORCEs Virtual Conference (you can watch it here), Dr. Susan Domchek of the Basser Center for BRCA at the University of Pennsylvania said of these liquid biopsy screening tests:

“We all want them to work...these tests are going to get better, but from what I've seen so far, these tests are not ready yet...Believe me, the minute we think these tests are good enough, we will roll them out to you!"

For this reason, most experts aren’t ordering these tests for patients. Nor have expert panels that set national guidelines added these tests to their recommendations.  

Other issues to consider

Finding cancer early is the key to improved treatments and extended survival. While it seems odd, finding cancers early is not always better. Some tumors may never grow enough to need any treatment. In this case, early detection might result in overtreatment.

False-positive test results are another major concern because they indicate that a tumor may be present, but none can be found. False positives can lead to needless anxiety and unnecessary additional procedures.

Cost is also an important consideration. These tests may cost hundreds of dollars. The current cost for Galleri, for example, is $949. Since these tests are not yet included in screening guidelines most health insurance companies don’t cover them for early detection.

As Dr. Domchek said, “These tests will get better.” As they do improve, insurance companies may be more likely to cover them, and out-of-pocket costs may go down. Now, however, people need to compare the costs and benefits of these tests. In the meantime, you might consider participating in a research study looking at early detection for cancer. Some research studies do not provide participants with the results of their tests, so if you do enroll in a study and knowing your results is important to you, be sure to ask if you will be given your results.

Media coverage is a problem

Hyped headlines describe Galleri as “revolutionary,” “groundbreaking,” “innovative,” “a once in a generation breakthrough,” “a new paradigm for cancer screening,” and, not surprisingly, the “Holy Grail” of oncology.

Gary Schwitzer, the founder and publisher of HealthNewsReview, notes that “…incomplete, fawning news coverage of health screening tests is one of the most clearly established problems in health news coverage.” Underlying this issue is the idea that the benefits of cancer screening have been historically overstated while the harms have been largely ignored.

Much of the media reported that Galleri correctly identified when cancer was present in 51.5% of cases, across all stages of the disease, and wrongly detected cancer in only 0.5% of cases. But there was no analysis of what those numbers mean to patients. Most of the media skirted the entire sensitivity issue. And most did not explain that the 51.5% sensitivity of the test—its ability to find cancer—means that almost 50% of cancers were not detected.

What's more, the test's sensitivity varies based on the type and stage of a cancer, which isn't optimal. For instance, Galleri has been shown to detect just 18.2% of kidney cancers compared to 93.5% of lung cancers. While overall it picks up 90.1% of stage 4 cancers, it only detects an average of 16.8% of stage 1 cancers. Yet it is being touted as a test that can detect cancer early.

The future of liquid biopsies

More well-controlled studies are needed, as well as expert evaluation of results to validate screening tests like Galleri before anyone can confidently declare that these tests benefit patients and improve outcomes.

The next few years could provide valuable answers toward the accuracy and acceptability of tests like Galleri. The U.K.’s National Health Service is conducting an ambitious 140,000-person, randomized trial of Galleri that should be particularly helpful in understanding how well the test can detect early-stage cancer.

Notably, liquid biopsies are also being looked at across many areas of oncology, including finding biomarkers for targeted therapies, monitoring treatment response and looking for evidence of recurrence earlier. The research is still very early, but very promising! Stay tuned!

Read more about liquid biopsies in our XRAY review.

Posted in: Risk Management , XRAY
Tags: Previvor , Screening And Prevention


March 15, 2023

Mark says:
I was quite disappointed that this test found no evidence of cancer, when MRI a few weeks later found the 2cm tumor on my pancreas. Quite a gut punch. Wish I could get my $950 back.


May 25, 2023

Mardie Geiser says:
I was part of a research study, so did not have to pay for the Galleri Test Kit. (I would not have paid to have it done). The result came back negative for me on June 20, 2022... 10 months later, on March 17 2023 1 felt a lump on my breast. I had surgery on May 4, 2023. They took out 7 nodes and a 2.2cm lump. Pathology stated clear margins and clear nodes. They stated I was a Stage 1. Also, I had a genetic test done, and that stated " Genetic Result: negative - no clinically significant mutation Identified. Thank god for Medicare - that test could have cost around $4,000. So I am not sure what I think about the Galleri Test, (0r the genetic test) ...brings to mind the debacle of "Theranos"


June 8, 2024

Denise Johnson says:
My friend is having this test done now. I had not heard of it but decided to check out the reviews. This product screams Theranos to me.


March 17, 2023

Charles Long says:
That's because it's a smaller cancer


July 29, 2022

Mia Evans says:
It's interesting to know that there are tests that are making headlines wherein it can detect cancers in their early stages. I can imagine how beneficial getting medical health testing with that kind of process to get treated as early as possible when you have been found with cancer. In my opinion, it is one of the most incurable health issues which is why detecting them earlier will give you more chances of getting better.


October 5, 2022

David says:
A test that can give you an early heads up 20-40% of the time compared to not knowing at all. What's the alternative, not knowing 100% of the time?


September 24, 2023

Chris says:
I'd rather have some chance of knowing early vs a zero chance of knowing early. Sure it isn't perfect, but antibiotics don't stop everything and yet we still use them. CPR is often unsuccessful, but we still do it.


October 7, 2022

Tom says:
You say it performs ‘poorly’ on early stage cancers. Compared to what? What is your alternative? And until it improves you’d rather know nothing at all? That’s nonsensical.


March 2, 2023

Julia says:
Just did one today and can’t be upset about a test that will in any way help early detection. I knew the limitations and feel it’s money well spent!


August 23, 2023

Diane says:
I have had this test for the last two years with no positive results, as recommended by my PCP. I have a cancer genetic, Lynch Syndrome. I suggested my boyfriend take the test, as we knew he already had prostate cancer and thought it a good idea to have an additional screening for anything else. HE CAME BACK NEGATIVE FOR ALL CANCERS AND HE HAD STAGE III PROSTATE CANCER!! They do advertise prostate cancer as one of the 50 they detect. If they can’t pick up a stage III aggressive cancer that they proclaim to identify, I am in fear for anyone who actually relies on the results!


October 3, 2023

Alex Janin says:
Hi Diane, I'm a reporter and I'd love to get in touch to learn more about your experience. Please let me know if you're up for it.


October 9, 2023

Alex Janin says:
Diane -- my email is [email protected]


August 2, 2022

Marnie Woodard says:
I've just read this article and I feel extremely betrayed especially since I just paid $950 for this test. I had no idea it was as unreliable as this article is saying it is and I am frightened for my health.


October 8, 2023

Jeffrey J Smith says:
Why can't there be fair, funded research into really detecting any energetics or RF signals or change in EM Fields in a cancer condition. We once had a Energy Medicine movement. Given the cost of cancer to society , Why can't there be well funded research in the that direction? Well, because you can't patent a frequency....


October 24, 2023

MC says:
@Jeffert J Smith... why cant they? Because they MAKE MONEY on keeping us sick. Why are so many food companies partnered with pharmaceutical companies? Why is organic(with that many less ingredients) so much more expensive? Why is a salad &12 but a big mack $7? Why are functional/homeopathic/naturpathic practitioners and treatments not covered by insurance companies? Why do government agencies proclaim "latest greatest breakthroughs and treatments", yet they do not administer these things to their own families? Follow the money, there's always an answer. Rothschilds. Rockefellars. Gates. They all play a role.


March 7, 2023

Anita Ingram says:
I just took this test and now await results. The rationale for taking is a strong prevalence and family history of various cancers. The biggest fear from this dialogue is false positives. I suppose the low stage 1 detection is problematic but it is better than nothing at all. It does give pause about the frequency of testing, however. Assuming it comes back negative when will I take it again? Similar to a colonoscopy, maybe wait 5 years? Especially given the cost. By then I would think testing reliability will have improved and more data will be available.


June 26, 2023

Marolyn Hundley says:
I just received the results of my Galleri test and it showed no cancer signal detected. I happy for the result as cancer runs rampant in my family.


March 22, 2023

Donna P. says:
It found my breast cancer metastases. I was already on a list for a Galleri study group due to family history. GP was treating me for arthritis when I was having hip pain. Breast MRI and x-rays showed nothing. Body PET scan located lesions on hip, back, and shoulder. I was post lumpectomy and radiation. I'm now being treated with Ibrance, Arimidex, and Zometa, and lesions are now clear on PET scan. It would've progessed further if I hadn't had the Galleri to detect it early, and if the genetics Dr. didn't recommended further imaging.


March 18, 2023

MJO says:
I'll take 70% of stage 2. With my family history, I welcome any help I can get.


January 18, 2023

annon says:
Be nice if they also focused on catching relapses of cancer early too.


May 1, 2023

Leslie Minion says:
I am part of the Pathfinder 2 study. I am a colon cancer survivor of 6 years. I signaled for possible Lymphoma or Melanoma. Bloodwork is mostly normal. SPEP and UPEP were inconclusive. PET scan showed multiple foci in many long bones. Abdominal MRI was suspicious for cancer but also not conclusive. Had a bone and bone marrow biopsy last week and awaiting results. Feels like I went down a rabbit hole! They should provide counseling while this is all going on! Grail is paying for all the testing so there's that. But the docs cannot figure out what I have. Don't think it's a false positive based on the PET but maybe so early that no one knows exactly how it would present? Ugh!!!


September 13, 2023

Brooke says:
Hi Leslie, did you ever get the results from your biopsy? Im curious because I am having a similar experience.


March 10, 2022

Patricia Walter says:
Thank you so much for this timely, and thorough discussion. This company was recently mentioned on my Facebook support group page for my type of cancer, so it was NOT the FORCE Facebook page. I will add a link to this discussion to my page.


March 11, 2022

Srivalli says:
This is really a informative thing which everyone need to know now-a-days This type of blood test really saves lives and also this would be easy to detect cancer at early stages <a href="">how to detect cancer early</a>


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