Is there a blood test that can screen for cancer?

This is a question I have heard repeatedly throughout my career. The answer always has been, “No, we don’t have that.” And I would describe how we have only a few cancer screening programs with proven merit that are used regularly in the U.S.:

  • Mammography for breast cancer after age 50.
  • HPV tests and Pap tests for cervical cancer, ages 25 and up.
  • Colonoscopies or stool testing for colorectal cancer in people over 45.
  • Low-dose CT scans can be conducted on people who are at high risk for lung cancer if they’re former smokers or have had occupational hazard exposure.
  • (PSA) tests screen for prostate cancer in certain populations. 

However, cancer is the second leading cause of death in adults, and the majority of cancer deaths are from cancers not screened for on the list above. It’s no wonder why the question keeps coming up.

“We don’t have effective screening for those,” is all I could reply. I would talk about the importance of living in a way that lowers the risk of cancer and paying close attention to symptoms. If a symptom ever becomes detectable we pursue targeted evaluations.

That’s what we did, and we did it that way for a long time.

All that is changing.

Life on earth is rapidly changing in the current moment and with it so are the stock answers to questions like the one above.

Now when I’m asked about a simple blood test to check for 50 different cancer types I will say, “yes, we have that.”

Enter the Galleri test

A novel approach “uses DNA sequencing technology to analyze DNA fragments circulating in the blood, also known as cell-free DNA (cfDNA). Both non-cancer and cancer cells release cfDNA into the blood, but cfDNA from cancer cells has methylation patterns that are specific to cancer. 

Machine learning and pattern recognition are used to identify abnormal methylation patterns that could signal the presence of cancer.

DNA methylation patterns are also organ and tissue specific. When a cancer signal is detected, Galleri analyzes DNA methylation patterns to predict the tissue or organ associated with the cancer signal (known as Cancer Signal Origin). The Cancer Signal Origin information can help guide the diagnostic workup to confirm the presence of cancer by standard medical practice.

The Galleri test is not a genetic risk assessment. A genetic risk assessment is a one-time-only measurement and assesses your future risk of developing cancer. The Galleri test looks for a signal associated with active cancer at the time of your blood draw.”

Its recommended use is to repeat annually.

Lots of nuances

The FDA approval process is underway but has not been completed.  Insurances are not covering it yet and no major medical organization currently recommends the Galleri blood test for cancer screening in average-risk, asymptomatic individuals.  Use of Galleri is not recommended in individuals who are pregnant, 21 years old or younger, or undergoing active cancer treatment. It’s a self-pay situation now and costs in the neighborhood of $1000. Galleri is not meant to replace the usual screenings but provides an interesting option for high-risk patients in certain scenarios as an add-on to current offerings.

My point is, it’s available. 

It’s not yet ready for use on a large scale, but it points to what is coming. Before it is useful for the masses it might be useful on a smaller scale, on an individual basis.

The main prerequisite for its use is to know its power and its limitations. Here are the main points to know about the test:

  • Galleri tests for 50 plus different types of cancers
  • It’s a screening test. A positive result means more exploration is warranted. With a positive test result, you also are told of the organ system where a possible cancer is located (the test is 89% effective in predicting where the cancer started).  More tests, like imaging tests, are needed to assess the situation after a positive test. 
  • Only about half the time will a cancer be found after getting a positive test. 
  • In their main study of 20,000 people, the cancer detection rate was 1%. The false positive rate was 0.5%. 
  • The test can also give a negative result when a cancer is present. In other words, it can miss it when it’s there. 
  • The Galleri test finds about half of cancers that are present in its participants. Traditional cancer screenings are still recommended concomitantly. 
  • In their study, a false negative test occurred less than 1.5% of the time. If a test yields a negative result 98.5% of participants did not have a detectable cancer.
  • The test’s tendency to detect cancers at an earlier stage compared to symptom-driven evaluation is a major benefit. Its other main benefit is that a wide variety of cancers are being evaluated.


It’s smart to be wary of being too far in the future too soon. Medicine, like society, is creating a wave of major change. The rate of change is fast, and it can feel chaotic. At the same time, we have to be wary about relying on yesterday‘s solutions. Early adopters have to deal with working the kinks out. Those who lag have safety on their side although at some point it is revealed as mostly illusory.

Through neutrality, we can tap into the place in the middle between the future and the past. Courage and trust open up this elusive but rewarding zone. It’s the place to build a command center to face the chaos of these times.

It is uncomfortable, but we have to go forward. If we lead with questions and only settle briefly with that moment’s answer we will remain on track.