Guardant’s blood test might replace biopsies for some lung cancer patients, study says
Could a blood test help more lung cancer patients get drugs that are targeted to the genetic weaknesses of their tumors?
Yes, according to summary results of a 282-patient clinical trial being made available Wednesday. The result is a boon for Guardant Health, the San Francisco-based startup that sells the test, Guardant360, which is a “liquid biopsy” that works by detecting fragments of DNA in the bloodstream. The full study will be presented in full at the annual meeting of the American Association for Cancer Research in early April.
All of the 282 patients had been newly diagnosed with non-small cell lung cancer. Each received both a traditional biopsy — a small amount of tumor tissue removed from the lung — and the Guardant blood test to try to identify if the patient’s cancer was driven by one of seven genetic alterations (EGFR, ALK, ROS1, BRAF, RET, MET, and ERBB2) that medical guidelines say should be treated with particular targeted drugs. These changes were detected in 60 patients, or 21.3 percent, via the biopsy method and 77, or 27.3 percent, of those who received the Guardant blood test.
In other words, the blood test was more likely to match patients with drugs. It was also much faster. Results arrived in nine days with the Guardant blood test compared to 15 for the biopsy patients, meaning that very sick patients could start treatment sooner.
The results, currently available only as an abstract, include another important detail: For the four genetic changes for which there are approved drugs (that would be EGFR, ALK, ROS1, and BRAF), a positive result using the Guardant blood test always correlated with a positive result via the biopsy.
“Every time,” said Dr. Vassiliki Papadimitrakopoulou, a professor at The University of Texas MD Anderson Cancer Center and the study’s lead author. “We think the practical implication that this provides about use is to make the liquid biopsy test potentially the first test for patients with non-small cell lung cancer.”
That could be commercially important to Guardant, which is facing big expectations from its investors (the company, which had sales of $50 million last year, sports a market capitalization of $4.7 billion), but also to drug makers that make medicines that target lung cancer. And it could be a big deal for patients, too many of whom don’t receive the genetic testing they need.
All of the genetic alterations being tested for are rare, but together they account for as much as a third of non-small cell lung cancer patients. What’s more, these patients don’t tend to respond as well to immunotherapy drugs like Merck’s Keytruda or Bristol-Myers Squibb’s Opdivo. And patients who receive medicines targeted to their disease, like Roche’s Alecensa for ALK mutations or AstraZeneca’s Tagrisso for EGFR mutations, can see their tumors shrink dramatically.
Helmy Eltoukhy, Guardant’s CEO, argues for a paradigm he calls “blood first.” It’s often hard to get biopsy tissue (in this study, six patients’ biopsies did not have enough material for tissue-based tests).
But Dr. Alice Shaw, director of the Center for Thoracic Cancers at Massachusetts General Hospital, says she wouldn’t be so fast to move to liquid biopsy. While genetic alterations found with liquid biopsy are almost certainly true, she says, there’s also evidence that the test can miss some patients. A recent paper by her group showed that the Guardant test missed patients with ROS1 rearrangements half the time, potentially depriving them of medicines like Pfizer’s Xalkori that can shrink their cancer. She notes, however, that as Massachusetts General results from biopsy tests come back very quickly, sometimes within days, she doesn’t routinely order both for fear insurers will not pay for both.
Shaw says, however, that she orders the Guardant test regularly, and she sees other doctors ordering it, too. She recounts a recent experience with a patient who had been referred from another hospital whose biopsy was taking a long time to come back and who was very sick. She ordered the Guardant test, and the EGFR result came back positive. “She came back with an EGFR. We are so excited, and we went ahead and treated her,” Shaw says.
Making testing a more regular occurrence for lung cancer patients will also be important for drug companies such as Roche, Eli Lilly, and Bayer, which are introducing new gene-targeted cancer medicines — that will only sell if patients with matching genetic alterations are found.
The Guardant360 has a list price of around $8,000, but Medicare pays about $3,500.
Originally published on statnews.com