‘ Coming into their own’: FDA approval of liquid biopsy tests puts early, less invasive cancer detection in broader reach
Cancer patients often have to endure months of anxiety and side effects before they can schedule a scan or painful biopsy to learn if their treatment is working.
Liquid biopsy tests, which won federal approval this summer, could make that process faster and less miserable.
The Food and Drug Administration approved Guardant360 CDx in early August for use in a range of solid tumors; Foundation Medicine’s FoundationOne Liquid CDx, became available for widespread use later that month.
The tests aren’t brand new, but the federal approvals will make them more accessible, as Medicare and more insurance companies cover the costs, which can run as much as $ 6,000.
“I think that liquid biopsies now are coming into their own,” said Dr. Matthew Freedman, an oncologist and researcher at the Dana- Farber Cancer Institute in Boston.
Targeting treatment
The newly approved liquid biopsies can identify the genetic signature of tumors, which then can be used to match patients to treatments or research trials with experimental therapies.
Lung cancer patients who have certain genetic mutations in their tumors, for instance, can double or triple their life expectancy when given a drug targeted to those mutations.
Doctors can also use liquid biopsies a few weeks after starting treatment to see how a tumor is evolving, and perhaps gain insights into why a treatment isn’t working, said
Helmy Eltoukhy, CEO of Guardant Health, of Redwood City, California, which makes Guardant360 CDx.
“It’s better care for patients at lower cost if you test appropriately,” he said.
Today, many cancer patients, particularly those with hard- to- reach tumors, get one biopsy with all future treatment decisions based on that one sample. But tumors change over time. “There’s almost no other area of medicine where you’d use an old clinical specimen to decide treatment,” Eltoukhy said.
Because blood is so easy to access, a liquid biopsy can be done several times to see how the tumor evolves, he said. And patients who live far from an academic medical center can still get cutting- edge recommendations without traveling.
Finding a needle in a haystack
Liquid biopsies are generally seen as not as precise as more typical biopsies, where a needle is inserted directly into a solid tumor. “If one had a choice, the choice would be to look at the biopsies,” said Dr. Bert Vogelstein, who has spent years developing liquid biopsy tests as a professor at Johns Hopkins University in Baltimore.
But with some cancers, it’s not easy to access the tumor, or there’s very little cancerous material that can be withdrawn or seen.
As a tumor begins to spread its tentacles, it’s initially invisible on scans. And after successful surgery, there may be no obvious tumor, but residual disease could still be lurking.
Liquid biopsies can fill those crucial gaps.
Scientific advances in recent years have made it possible to identify cancer DNA in the bloodstream — tiny needles in the haystack of the bloodstream.
This opens up a lot of possibilities for treatment and diagnosis, Vogelstein said.
In colon cancer, for instance, roughly half of Stage 3 patients who otherwise would die can be cured with so- called adjuvant therapy, Vogelstein said. But nearly everyone who has enough metastatic cancer to be visible on an X- ray will die from their disease. “You cure close to 0% with adjuvant therapy,” he said.
Adjuvant therapy is terribly toxic, though, so doctors don’t want to use it unless they believe the patient is likely to have metastatic disease.
“So, this is a decision that virtually every patient goes through: Should I undergo adjuvant therapy?” said Vogelstein.
Until now, they’ve only been able to guess and play the odds. But early research suggests using liquid biopsy to identify if there’s residual disease can help make that decision easier, Vogelstein said.
Although studies proving the clinical usefulness of liquid biopsies have yet to be completed, he added, “Patients with positive liquid biopsies after surgery nearly always recur, and many that don’t have
positive liquid biopsy tests don’t recur.”
Doctor and patient perspective
Dr. Neal Shore, medical director of the Carolina Urologic Research Center in Myrtle Beach, South Carolina, said he uses liquid biopsies to help him find clinical trials for patients with advanced cancer.
One patient, who only wanted to be identified by his first name, Joel, has been on a clinical trial of a double- drug therapy for two years, after a liquid biopsy identified a genetic mutation in his advanced prostate cancer.
“He looks great,” Shore said on a call with Joel and his wife Tracey. “He’s done exceptionally well.”
Joel said the treatment has been challenging at times. He has trouble swallowing some days, suffers from back pain and the hormone therapy he still takes gives him hot flashes.
But his wife said his issues are largely manageable with Tylenol and heating pads. “For the most part, he feels pretty good,” she said.
Shore, who treats patients with kidney, bladder and prostate cancers, said liquid biopsies are particularly useful when a tissue sample is old or unusable.
“It expands our treatment armamentarium,” he said. “This is really exciting for me as a urologist.”
Hope for the future
The next step, said Cindy Perettie, CEO of Cambridge, Massachusetts- based Foundation Medicine, will be to use liquid biopsies early in the course of someone’s treatment.
“We’re really focused on taking it from the metastatic setting and moving it to the early setting,” she said. “That’s where we’re going to have the opportunity to really impact ( patients).”
Breast cancer patients on maintenance therapy with tamoxifen, for instance, usually have to wait five years to know if their cancer has advanced, she said, but a liquid biopsy could let them know much faster and more often.
“We can look every six months whether they’ve progressed or not,” Perettie said.
Even further into the future, the real potential for liquid biopsies lies in early detection.
For kidney cancer, as well as many other tumors, the earlier the diagnosis, the better the chance of survival, said Freedman of Dana- Farber. He, along with colleagues including Dr. Toni Choueiri, showed in a paper published earlier this summer they could identify kidney cancer cells in urine at all stages of disease.
If such tumors could be identified when they’re just beginning, the prognosis for kidney cancer would vastly improve.
“You want to cure cancer. You don’t cure it with third- line chemo. You want to cure it before it happens,” Choueiri said.
Today, about 20% of cancers are diagnosed via screening tools like mammography, colonoscopies or stool- based tests. Add liquid biopsies and that figure could jump to 75%. “I think that will be possible within five years or so,” said Vogelstein, who is involved in a company, Thrive Earlier Detection, based in Cambridge, Massachusetts, that is working on such a test.
The challenge: the smaller the tumor, the less DNA released from the cancer cells, so the harder it is to detect.
Metastatic cancers that have spread throughout the body might account for 5- 10% of the DNA floating in the bloodstream; but DNA from very early tumors may make up just 1- in- 10,000 or 1- in100,000 DNA molecules in blood, Vogelstein said.
Studies have shown it’s feasible to find these few needles in a haystack but not whether it’s useful to doctors or patients.
There is also a risk to using liquid biopsies as a screening tool for early tumors, Vogelstein warned. False positives — telling people they have cancer when they don’t — could do a lot of harm.
And a liquid biopsy can only say there’s a high likelihood someone has cancer somewhere — and that further testing is warranted, he said. Sometimes, something might look like cancer on a CT scan, but it isn’t.
“It is essential,” he said, “to show that the benefits of early detection outweigh the risks.”