By Steven Reinberg
According to investigators, the test is as effective as a tissue biopsy in diagnosing advanced non-small cell lung cancer, by far the leading form of the leading cancer killer.
The so-called "liquid biopsy" can also quickly identify tumor gene mutations that match targeted drug therapies -- potentially boosting patient survival.
The new findings present "a convincing argument for use of the liquid biopsy as a first option for molecular testing in advanced non-small cell lung cancer," said lead researcher Dr. Vassiliki Papadimitrakopoulou. She's professor of thoracic head and neck medical oncology at the University of Texas MD Anderson Cancer Center.
As the Houston team explained, if a CT scan suggests lung cancer, patients are typically asked to undergo a surgical tissue biopsy. It's an expensive, invasive procedure that comes with risks and inconvenience to patients.
Seeking a way around these procedures, numerous companies have been developing blood-based diagnostic tests for lung cancer. The new study focuses on one such test, called Guardant360, developed by Guardant Health, the company that funded the new study.
Blood tests like Guardant360 rely on traces of tumor DNA in blood for clues to the presence of lung cancer and the best way to treat it.
In addition to the higher accuracy found in the new study, the researchers reported that the results of the blood test can be turned around sooner than those of a tissue biopsy.
While results for a standard biopsy took 15 days to process, results of the liquid biopsy took just nine days, on average, the study found.
That means treatment could begin sooner, with potentially better outcomes, the researchers said.
Speedier genetic analysis of the tumor is crucial, the investigators explained, because 30 percent of lung cancers can now be successfully treated with new gene-targeted medicines. These drugs tend to have higher response rates than standard chemotherapy.
For the study, Papadimitrakopoulou and her colleagues used Guardant360 to identify mutant genes in the blood of nearly 300 patients.
Specifically, the tests were focused on seven "biomarkers" in blood samples -- tumor-specific gene mutations that can help identify subtypes of lung cancer.
The Guardant360 test also looked for one biomarker -- called KRAS -- that helps predict a cancer patient's prognosis, the research team said.
The blood test seemed to outperform standard tissue biopsy. While the standard surgical biopsy found at least one marker predictive of lung cancer in 60 patients, the blood test spotted it in 89 patients, the findings showed.
Drugs that target many of these lung tumor gene mutations are already approved by the U.S. Food and Drug Administration, the researchers noted.
Among the more than 190 patients who did not show the presence of one of the seven genetic tumor biomarkers, testing was often still able to spot the KRAS prognostic biomarker, the study team said.
Again, the blood test beat tissue biopsy in this regard: The Guardant360 test spotted the KRAS biomarker in 92 patients, compared with 24 patients who underwent standard biopsy.
Still, the new study was limited in two ways. First, Guardant360 results weren't compared to the results of the very latest gene-based surgical biopsy analyses. And secondly, the results apply only to the Guardant360 test -- not to other liquid biopsies already out there.
One lung cancer specialist was still heartened by the results, however.
"For years, we have been doing surgical biopsies, but over the last few years there's been a recognition that this is more a 'molecular disease,' governed by [gene] mutations," said Dr. Richard Lazzaro, chief of thoracic surgery at Lenox Hill Hospital in New York City.
It's also been known that cancer cells can shed their DNA into the blood, he said.
"If you can make diagnosis and treating decisions and save time, that's outstanding for patient care," Lazzaro said.
Effective treatment, delivered sooner after diagnosis, should improve survival, he added.
Already, liquid biopsies are often being used in tandem with surgical biopsies, Lazzaro noted.
However, "perhaps one day they will replace a surgical biopsy and may become a better therapeutical paradigm," he said.
The results of the study are to be presented March 29 at the American Association for Cancer Research meeting, in Atlanta. Findings presented at medical meetings are typically considered preliminary until published in a peer-reviewed journal.
According to the American Cancer Society, lung cancer remains the number one cancer killer in the United States, with nearly 143,000 deaths expected in 2019.