The vision of a single blood test that could screen for dozens of different cancers has tantalized oncologists formore than a decade.
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The science has advanced at a rapid clip: What began by analyzing levels of proteins in the blood has progressed to scrutinizing tiny amounts of DNA and feeding the data into algorithms that can highlight changes suggestive of cancer.
It’s led to a number of eye-catching developments. Inone study, a blood test called Mercury was able to correctly identify 13 cancers with an average of 87% accuracy, including 77% of stage 1 cancers.
“It’s amazing we can even do this,” says Dr. Aadel Chaudhuri, a radiation oncologist at the Mayo Clinic in Rochester, Minnesota, who himself is researching multi-cancer blood tests. “If you had asked me 10 years ago, my answer would have been ‘It’s not feasible.’ If we’re thinking of DNA shed from a small tumor, it’s like being on the beltway in D.C. and you’re looking for one Volkswagen.”
The ultimate hope is a test that would be able to accurately detect a range of cancers at an early enough stage where they are still curable. That would translate into lives saved.
But in February came disappointing news: The largest trial to date on cancer blood tests failed to achieve its primary objective. The trial was run by Grail, a biotechnology company that manufactures a test called Galleri that, it says, can detect more than 50 different types of cancer through measuring DNA fragments in the blood.
But the trial results,released by the company, saw no significant reduction in advanced cancer diagnoses in people who received the Galleri test compared with those who had not.
“It’s hard to argue that it wasn’t a setback,” Chaudhuri said, who wasn’t involved with the trial. Still, it’s premature to dismiss the trial as a total failure, he said. The full results have not yet been published and it did appear that, in some cancer types, the test had helped detect more cancers at the earliest stages, while the numbers of stage 4 diagnoses — cancers which have spread to distant organs and are considered incurable — decreased. “Clinically, what I truly care about is a decrease in stage 4 cancers,” Chaudhuri said.
Dr. Deb Schrag, a medical oncologist at Memorial Sloan Kettering Cancer Center in New York City, said that for multi-cancer blood tests like Galleri to be seen as a paradigm shift by the medical profession, they will need to demonstrate that they can help save lives. Grail will continue to follow patients from its trial for up to eight years after they got their first test to monitor if there has been any reduction in deaths.
Source: Drudge Report
