Guardant’s Cancer Blood Test Matches Tissue Biopsies in Trial

A large-scale study comparing Guardant Health Inc.’s blood test to tissue biopsies showed that results were closely matched. The findings may help doctors feel more confident in using the blood test as a non-invasive alternative to traditional biopsies, according to the startup.

Researchers used blood samples from more than 15,000 advanced cancer patients and compared the frequencies of mutations in specific tumor types to previously published data from genomic analyses of tumor tissue, such as from the Cancer Genome Atlas. The frequencies were closely correlated, according to data presented Saturday at the annual meeting of the American Society for Clinical Oncology in Chicago.

Of the 386 patients whose tissue and blood samples were both available, accuracy of the blood test was 87 percent, according to the study’s abstract. In lung, breast and colorectal cancers, the results were 86 percent, 83 percent and 85 percent, respectively. The accuracy rate was 78 percent for the other cancers in the group.

The promise of a so-called liquid biopsy test is to provide a cheaper, less intrusive way to track how a cancer is mutating or responding to treatment. The tests screen the blood for tiny fragments of genetic material released by cancer tissue, known as circulating tumor DNA. Such tests have only recently become available as genetic sequencing has become more affordable and the technology has improved so much that it can detect just a few molecules of errant DNA in a vial of blood.

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“It’s by far the largest liquid biopsy study ever done,” said Helmy Eltoukhy, chief executive officer of Guardant. The startup, backed by investors including OrbiMed Advisors, Khosla Ventures and Sequoia Capital, is one of the front-runners in the space. “The study puts to rest a lot of unresolved questions about whether liquid biopsies are clinically relevant.”

Guardant is running further trials to evaluate its test’s accuracy in earlier stage cancers and its ability to detect recurrence of cancer after a patient finishes treatment, Eltoukhy said.

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