The Galleri Test: Introduction
Did you know that 71% of cancer deaths are from cancers not commonly screened for? That’s where the Galleri Test comes in and provides promise for detecting these unscreened cancers early in their course so that early treatment can be initiated. Why is this important? When cancers are diagnosed early before they had a chance to spread, the overall five-year survival rate is four times higher than when diagnosed in later stages. More specifically, the 5-year mortality rated is 11% for cancers detected early versus 79% for cancers when detected late.
Before discussing the Galleri Test further, what are the five cancers that we screen for routinely?
The 5 Cancers and Routine Screening
There are five cancers that are routinely screened for today. These include:
- Breast cancer with mammography.
- Cervical cancer with Pap and HPV test.
- Colorectal cancer with colonoscopy and various stool tests.
- Lung cancer with chest x-ray and low-dose CT imaging.
- Prostate cancer with digital rectal exam and PSA level.
The recommended frequency for screening for these cancers varies by the type of cancer. In addition, cancer screening frequency does change as we learn more about each cancer and the effectiveness of the screening test. Generally speaking, we screen for cancers that can be detected early and for which there are effective treatments.
Unfortunately some cancers are frequently detected too late. For some cancers, by the time patients have symptoms, the cancer has already spread. Pancreatic cancer is a good example of such a cancer and has very poor survival rate even today that have not changed much in decades.
The Galleri Test is not intended to replace the screening tests for the 5 cancers we already screen for with other methods.
The Galleri Test: Details
The Galleri Test is made by Grail® and screens for over 50 cancers including the five cancers mentioned above. It is most effective in detecting cancers that tend to grow quickly. It detects DNA changes produced by cancerous cells that make their way into the bloodstream. So what are these 50 cancers?
- biliary cancers
- bone cancer
- breast cancer
- cervical cancer
- colorectal cancer
- esophageal cancer
- gallbladder cancer
- gastrointestinal stromal cancer
- gestational trophoblast neoplasms
- kidney or renal cancer
- laryngeal cancer
- lung cancer
- lymphoma: Hodgkin’s and non-Hodgkin’s
- Merkel cell carcinoma
- nasal cavity cancers
- nasopharyngeal cancers
- neuroendocrine tumors of appendix and colon and pancreas
- oral cancers
- ovarian and Fallopian tube cancers
- pancreatic cancers
- penile cancers
- plasma cell myeloma
- prostate cancer
- small intestine cancers
- sarcoma of abdomen and visceral organs
- sarcoma of the head and neck
- the trunk and extremities
- stomach cancer
- testicular cancer ureter cancer
- uterus cancer
- vaginal cancer
There are various subsets of some of these cancers taking the number to 50 cancers.
How Does the Galleri Multi-Cancer Detection Test Work?
The Galleri Test involves a simple blood test. The test must be ordered by a physician. The Galleri Test looks for signals in the blood to see if any of those signals are coming from cancer cells. All cells (healthy and cancerous) release DNA into the blood stream. The DNA from cancerous cells differs from the DNA of healthy cells. The Galleri Test can detect this abnormal DNA from cancerous cells and predict where (organ of origin) in the body it is coming from with high accuracy. Your physician can then hone in on the likely source of the cancer with imaging studies such as CT scan, PET scans, or MRI scans, plus additional blood work.
The test is indicated for those at high risk of cancer such as those over age 50, those with a personal history of cancer, and those with a family history of cancer. People age 50 and older have a 13 times increase risk of cancer.
The Galleri Test could detect 3 times as many cancers if the test were added to guideline-recommended cancer screenings.
How Accurate is the Galleri Multi-Cancer Early Detection Test?
The Galleri Test has been study in clinical trials involving over 50,000 participants. To put this in perspective, there are typically several hundred to 3,000 participants in a clinical drug study.
There are two features of any test that are important in determining how accurate a test is or how well it discriminates individuals with a disease from those without the disease. The two parameters are the sensitivity and the specificity.
Sensitivity tells us the percentage of the individuals with disease who actually have an abnormal test result. Specificity tells us the percentage of those without disease who have a normal test.
The Galleri Test has a sensitivity of 76.3% for cancers that cause two-thirds of cancer deaths. Therefore, it does not pick up all cancers. This is one reason it is not a substitute for the screening tests used for the five cancers we discussed above. One of its main benefits is detecting, hopefully early, the other cancers that cause most of the cancer deaths.
The sensitivity is determined by the strength of the abnormal signal of cancer DNA in the blood. The more abnormal DNA shed into the blood, the more likely the Galleri Test will detect it.
The Galleri test is highly specific. It’s specificity rate is 99.5%. This means that a positive test result is likely to be accurate and not represent a false positive. Only 1 in 200 positive test results would represent a false-positive test.
There is a third feature of the Galleri Test. The Galleri test is 89% accurate in determining of the origin (organ) of the abnormal DNA signal of cancerous cells. This then enables your physician to follow up with other tests honing in on the likely origin of the cancer cells. This facilitates early treatment of the cancer. The goal is to detect cancers long before patients show symptoms.
What is the Cost of the Galleri Test?
The Galleri test costs $949. You may be able to use your HSA or FSA accounts to pay for the test which at this time is not covered by insurance.
The Galleri Test tells you with high degree of accuracy if you have cancer at the time of the test. You could have a negative test today but an abnormal test in 1-2 years. Therefore, it is necessary to repeat the test periodically as part of an ongoing cancer surveillance program. The Galleri test does not assess for genetic mutations like the BRCA1 and BRCA2 gene mutations that are associated with certain cancers and can be passed on from generation to generation. These types of genetic tests only have to be done once as opposed to the Galleri Test.
So the cost and the need to periodically repeat the test are drawbacks to the Galleri Test, but may well be worth it for those at high risk for cancers such as pancreatic and ovarian cancers which are frequently discovered only at advance stages.
Test results are available in 2 weeks. We recommend you speak to your physician for more information about this cancer surveillance tool.
Article updated 1/12/23. Originally published 2/26/22.