Cancer remains one of the leading causes of death in the United States, accounting for nearly 1 in 5 deaths
As primary care providers, we have a very important role in helping patients understand what screenings are available, what they detect, and how we can find cancers as early as possible—when treatment is most effective.
Today, we have two major categories of cancer screening:
- Traditional, guideline-based screenings
- Newer multi-cancer early detection (MCED) blood test
Let’s walk through both.
Traditional Cancer Screenings (Still Essential)
Standard screening tests are recommended based on age, gender, and risk factors. These include:
- Mammograms (breast cancer)
- Colonoscopy or stool-based testing (colon cancer)
- Pap smear / HPV testing (cervical cancer)
- PSA blood test (prostate cancer)
- Low-dose CT scan (lung cancer for high-risk smokers)
These tests are backed by years of research and are proven to reduce cancer deaths. They are usually covered by insurance.
Fortunately, these standard tests do screen for the four most deadly cancers- Breast, Colon, Prostate, and Lung (if tobacco user).
The Challenge: Some of the Deadliest Cancers Have No Routine Screening
Cancers of the liver, esophagus, stomach, pancreas, ovary, lymphoma, and plasma cell systems rank just below the four most deadly cancers. We have no screening for these cancers, and unfortunately, they are detected late in the disease state when treatment is more difficult. We can add lung to that list because it is the most common and deadly cancer, and even though we have good screening for tobacco users, there is no recommended screening for non tobacco users.
This is where newer blood-based screening technologies are generating interest.
Multi-Cancer Early Detection (MCED) Blood Tests
MCED tests are designed to detect signals of cancer in the bloodstream before symptoms develop.
Three of the companies currently offering these tests are:
- Galleri
- Cancer Guard (by Exact Sciences)
- Guardant Health (Shield Test)
How Do These Tests Work?
Cancer cells release DNA and proteins into the bloodstream. These tests look for DNA and these proteins that are being shed from the cancer cells.
Galleri
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- Tests methylated DNA
- Includes testing for 50 cancers
- Has higher sensitivity for:
- GI cancers of Pancreas, esophageal, gastric, and liver
- Ovary
- Lymphoma, and Plasma cell cancers like Multiple Myeloma
- Lung
- Often better at identifying the likely cancer type and location
- This test has the highest overall ability to detect cancer, has the most data, and the lowest false positive rate
- The cost is about $800.00
Cancerguard (Exact Sciences)
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- Tests methylated DNA + cancer-associated proteins so it has two ways of looking for cancers
- Tests for 50 cancers
- Does not test for breast or prostate cancer
- The cost is similar to Galleri
Guardant (Shield Test)
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- FDA approval for its blood test for colon cancer testing. (But this test is not as accurate as Cologuard or a colonoscopy.) For this reason, the insurers will pay for this test and not the other tests
- Nine other cancer screening tests that they package (including pancreas, liver, esophagus and stomach) at no additional cost
- Their test for esophagus and gastric cancers is the best at detecting this cancer
- Has a higher false positive rate, 3x that of Galleri
Important to Know:
In summary, we want to emphasize the importance of staying up to date with your recommended standard cancer screenings. Your annual physical exam is an excellent time to review which screenings are appropriate for you. It is also an opportunity to discuss these new supplemental blood tests that may help detect cancers for which no routine screening currently exists. The goal is simple: finding cancer earlier improves the chances of successful treatment and cure.
To help simplify the decision about these newer screening options:
If you prefer a test that is likely covered by insurance that focuses on a smaller group of gastrointestinal cancers, the Shield test may be a good option. It has particularly strong detection rates for esophageal and gastric cancers, although its false-positive rate is about 3x higher than Galleri.
If you prefer broader screening for multiple cancers, Galleri or Cancerguard offer testing that screens for approximately 50 types of cancer with generally strong performance.
Based on currently available data, Galleri appears to have the best overall balance of detection accuracy and the lowest false-positive rate. Its only notable limitation compared with Shield is slightly lower detection rates for esophageal cancer.
A quick note about results: a negative result is very reassuring. All of these tests have a very high Negative Predictive Value, which means if your test is negative, it is very unlikely that cancer was detected at that time.
If a test comes back positive, it does not automatically mean you have cancer. Instead, it means the test detected a signal that needs to be looked at more closely. In that case, we would recommend additional imaging or testing to better understand the result.
If you have questions about these screening options or would like to discuss whether one is right for you, please contact our office to schedule an appointment with your provider.
Let’s all help each other stay healthy!
