Cancer is easier to treat when detected at an early stage, and while effective screening methods are available for several cancer types, not everyone takes advantage of them. Making screening easier and as non-invasive as possible, such as with a simple blood test, might encourage more people to do so. That’s why the Galleri blood test, which the developers say can detect up to 50 cancers from a single blood sample, has been getting a lot of attention.
What is the Galleri Test?
The Galleri test detects what is known as circulating tumor-derived, cell-free DNA (cfDNA), which can indicate the presence of cancer. The DNA in malignant cells carries cancer-specific signals that are shed into the blood. Multi-cancer detection tests can then detect DNA fragments and their cancer-specific signals in the blood samples and locate where the signal originated in the body.
The appeal of the Galleri test is not only the simplicity of it, but also the number of cancer types that it can potentially detect. Thus far, the United States Preventive Services Task Force (USPSTF) only recommends routine screening for five cancer types (colon, breast, cervical, prostate, and lung cancers), while Galleri can detect those along with 45 others that do not have a recommended screening test available.
Can the Galleri Test Be Used Now?
You may be wondering, does it live up to its promise, and is it ready for “prime time” use?
The research has been thorough and is ongoing. The latest results from the PATHFINDER study, in which the test was used in 6621 healthy people ages 50 years and older, detected a potential cancer in 92 persons. Further testing confirmed cancer in 35 people, or 1.4% of the group. Importantly, while the test identified tumors in the breast, liver, lung, and colon, it also flagged ovarian and pancreatic cancers, which are generally diagnosed at a late stage and have poor survival rates.
It’s not foolproof, however. There was a high rate of false positives, as only about 38% of those who had a positive test turned out to have cancer. The manufacturer also concedes that the test is not yet ready for widespread population screening. They recommend its use in adults who are at a higher risk for developing cancer, and that it should be used in addition to routine cancer screening tests that are recommended by a healthcare provider.
Lecia Sequist, MD, MPH, director of the Center for Innovation in Early Cancer Detection from Mass General Cancer Center in Boston, agrees. “While the idea of screening for multiple types of cancer with a single blood test is very exciting and appealing for the public, in my opinion, the available tests are not quite ready for prime time just yet,” she said. “The data researchers have presented thus far have shown that a positive result on the blood test is still much more likely to be a false positive than a true positive indicating cancer.”
More needs to be done to learn how to select appropriate patients to undergo this test and what to advise patients and doctors to do next in the case of a positive test, she added. “I am hopeful that participation in research studies will continue to be vigorous, so that as a community we can all learn quickly how best to use these types of novel cancer screening tests,” said Dr. Sequist.
How Can I Access the Galleri Test?
The Galleri test is already available in the U.S. and is being offered by several health networks. But since it is not approved by the U.S. Food and Drug Administration (FDA), testing is not covered by health insurance, so individuals must pay about $950 for it out of pocket.