- An FDA panel recommended approval of a blood test that looks for signals associated with more than 50 cancer types.
- Blood tests have expanding uses, but important limits.
- Blood tests are a tool, but sometimes more an indication than an answer.
A panel that advises the Food and Drug Administration has recommended it approve the Galleri blood test by biomedical company Grail. The test is designed to search for signals associated with more than 50 cancer types and, when a signal is detected, predicts its likely origin. It does not establish a cancer diagnosis, which requires further testing.
Routine is becoming a less apt word to describe what blood testing can do. Many adults have rolled up their sleeves for a blood draw to find out their cholesterol levels or whether their thyroid is under- or overactive or if they are anemic or have diabetes, among scores of other stories a blood test can tell.
But the list of possible detections from blood has been growing for years with a steady stream of advances. Older tests that find signs of infection or liver or kidney function have been joined by other blood tests, most of them targeting specific diagnosis.
And like Galleri, if it is approved, many of those tests are a first step, rather than a diagnosis. For instance, last year the FDA cleared a blood test called Lumipulse that shows whether there are amyloid changes in the brain that could indicate the presence of Alzheimer’s disease. The regulatory agency cleared it as a complementary test to help diagnose Alzheimer’s in people 55 and older who have evidence of some cognitive decline, but emphasized that it’s not a stand-alone test for the disease and it isn’t to be used as a broad population-screening tool.
Neither test alone establishes a diagnosis. Results must be interpreted along with other clinical information, with additional diagnostic testing as needed.
The stories blood can tell
Cleveland Clinic points out that blood tests already exist to help evaluate and monitor some cancers, including liver cancer, thyroid cancer, ovarian cancer, breast cancer, testicular cancer and prostate cancer.
Tumor-marker tests measure substances that may be associated with cancer, but the results generally must be considered alongside imaging, biopsies or other tests, according to Cleveland Clinic.
A decade ago, the FDA approved a “liquid biopsy” blood test to identify patients with metastatic non-small-cell lung cancer who would likely be helped by treatment with the drug Tarceva. The blood test looks for specific changes in the epidermal growth factor receptor, or EGFR, gene which is the drug’s target, as the American Association for Cancer Research explains. The test does not screen for the cancer, but rather helps select treatment.
Cleveland Clinic lists blood tests that can help detect or monitor diseases, check organ function and measure levels of substances in the bloodstream. Among their uses:
- Anemia
- Blood disorders or cancers
- Diabetes
- Abnormal calcium levels
- Kidney function
- Liver function
- Sodium levels
- Carbon dioxide levels
- Potassium levels
- Chloride levels
- Certain bone disorders
- Specific vitamin levels, such as vitamin D
- Autoimmune disorders including rheumatoid arthritis or lupus
- Inflammation markers
- Blood-clotting disorders
- Red or white blood cell counts
- Pancreas function
- Heart failure or other cardiac issues
- Blood alcohol levels
- Iron levels
The list is not exhaustive by any means.
Blood tests can also help diagnose infections, including HIV, hantavirus, Ebola, listeria, salmonella, West Nile virus and more.
Opposition to the Galleri test
Grail said the Galleri test looks at DNA fragments in blood to find a “shared fingerprint” of various cancers before symptoms appear. If a “cancer signal” is found, it predicts the “cancer signal origin.”
From there, patient and healthcare providers have to use more standard means to confirm a diagnosis. There have been both false positives and false negatives in trials.
According to NPR coverage of the FDA advisory committee meeting, Galleri was recommended, but not without some opposition. The Galleri tests sometimes failed to detect cancers, especially those in the early stage, which concerned some of the advisers. “Phil Castle, director of the National Cancer Institute’s Division of Cancer Prevention, told the panel that the tests could do more harm by giving people a false sense of security, especially as it pertains to claims of ‘early’ detection. Castle told the panel the data on Galleri’s performance were too premature to prove the tests would be of any clinical benefit.”
He said, “Routine approval and broad population rollout would risk harm and waste resources.”
The article said the panel recommends Galleri marketing efforts include “specific recommendations to continue other routine cancer screenings and avoid characterizing the tests as ‘early’ detection tools.”
Galleri is not the only blood test being developed as a tool to find evidence of cancer. NPR reported that if the FDA approves Galleri, insurance companies might opt to pay for it. Right now, it’s available by prescription for a list price of $949.
Per The New York Times, “Oncologists and screening experts have expressed concerns that Grail’s test has not been shown to reduce cancer deaths, and they have warned that the possible risks, including harm to patients and increased healthcare costs, may outweigh any potential benefits.”
Ultimately, it will be up to the FDA to decide whether the test is approved. And no timeline for an FDA decision has been indicated.