Jim Ford, a 76-year-old retired car salesman, had been out golfing a week before his diagnosis. He had no symptoms. But he was in a trial for a blood test that screens for cancer, and in October 2020 it flagged stage two pancreatic cancer.
Surgeon Phyllis Napoles at Sutter Health in Sacramento removed his tumor, which was about the size of his thumb. A year after surgery, radiation and chemotherapy, Ford was cancer-free. Once symptoms appear, Napoles said, survival from pancreatic cancer can be as low as 3 percent. “This is so dramatic,” she said. “This is really going to change all the statistics we have on pancreas cancer survival and detection.”
The test is called Galleri, from the California company Grail, and it is one of a growing number of liquid biopsies, blood tests that pick up cancer signals circulating in tiny amounts. National Geographic reported in April 2021 that a dozen or more companies were working on such tests.
From treating cancer to finding it
Liquid biopsies began as a way to study the blood of people who already had cancer. As tumors grow, some cancer cells die and shed DNA, and the tests detect that circulating tumor DNA. Doctors use them to see whether a cancer carries mutations that a drug can target, to follow how a tumor responds to treatment and to spot relapse. The newer tests try something harder: finding cancer in people who have never been diagnosed.
The need is plain. In the United States, screening exists for five cancers: breast, colon, prostate, cervical and lung. Yet of the roughly 600,000 cancer deaths each year, more than two-thirds come from cancers with no good screening option, studies show.
The technical problem was the haystack. “You’re hunting through the haystack of DNA for the needle,” said Geoff Oxnard of Foundation Medicine.
Two approaches
CancerSEEK, developed at Johns Hopkins University, looks for known cancer mutations and for proteins that rise in response to a tumor. In a yearlong trial of about 10,000 women aged 65 to 75 with no history of cancer, an early version detected 26 cancers. Just 0.22 percent of participants had false positives that led to unnecessary and invasive procedures. The test is not available outside trials.
Galleri takes a different route. It looks for methyl groups that attach to DNA and switch genes on or off. Mutations can show up as a normal part of aging, said Joshua Ofman, Grail’s chief medical officer, but methyl markers are far more common, and that makes them easier for machine-learning algorithms to read. The patterns can also hint at where in the body a cancer sits. The company says the test can detect 50 types of cancer.
In a validation study of more than 15,000 people, the false positive rate was 0.5 percent. In an interim analysis of a trial of more than 6,600 people over 50, Galleri found 29 cancers of 13 types, and 40 percent of them were still at stage one or two. When the test came back positive, cancer was confirmed 44 percent of the time.
The caution
Doctors are not unanimous. Shivan Sivakumar, a medical oncologist at the University of Oxford, said it is important to get excited about these tests, “but you really do need to know if what we’re doing is actually working or not. I probably still sit on the fence.”
The worries are specific: false positives that lead to risky follow-up tests, early cancers that might never have needed treatment, and cancers with no effective treatment. DetecTogether, a cancer awareness group, noted in 2024 that the FDA has not approved these multi-cancer tests, that a positive result needs confirmation with further screening and possibly a tissue biopsy, and that a negative result can miss cancer. They are mostly an out-of-pocket expense.
In England, the National Health Service is working with Grail to enroll 140,000 people in a study of how the test performs. In the US, Galleri is sold by prescription for as much as $949. Anyone considering a multi-cancer blood test should talk to their doctor first.
Sources
- Innovative new blood tests could detect cancers early. When will they be ready?
- Multi-Cancer Early Detection (MCED) Tests: False Positives & Future Promise – DetecTogether
