There's a race on to develop blood tests for cancer -- but many doctors are still sceptical of them

Precision medicine — like cancer treatment that is tailor-made for an individual patient — is becoming more of a reality.

Critical to this is the ability to test people for characteristics of their disease that are unique to them. When it comes to cancer, the hope is that test’s called liquid biopsies — which use blood samples — will make this possible.

New data released Saturday at the American Society of Clinical Oncology annual conference in Chicago took a look at how liquid biopsies could influence how we treat cancer.

These tests rely on something called “circulating tumour DNA”, or the bits of DNA that are released from dying tumour cells into the bloodstream. Knowing what abnormalities a specific tumour possesses could help link cancer patients to treatments that specifically target those mutations as a more effective way approach cancer treatment.

Because tumours can change over the course a person’s illness (for example, once it becomes resistant to certain drugs), the idea is that liquid biopsies will allow for more frequent testing so oncologists can keep up with changes in the disease. A more traditional biopsy, which involves removing part of a person’s tumour, can be invasive and is usually conducted just once or twice.

What a blood test for cancer can tell you

Looking at more than 17,628 samples collected from 15,191 patients using a test from liquid biopsy company Guardant Health, researchers from Guardant and University of California-Davis found that, for the majority of patients, the liquid biopsy tests could sequence the tumour’s genome as well as a solid-tumour biopsy could.

But the study did show some limitations: liquid biopsies were only able to pick up circulating tumour DNA mutations in 83% of the samples. The rest were too hard to detect, especially when it came to patients with brain tumours, which the researchers attributed to the DNA not being able to pass the barrier that keeps the contents of blood separate from the brain (known as the blood-brain barrier).

It’s a shortcoming that means, that for now, for some tumours, oncologists can’t depend on liquid biopsies on their own.

“That’s nothing different than I knew six months ago,” Dr. Edward Kim of the Levine Cancer Institute at Carolinas HealthCare told Business Insider. Guardant’s test at the moment looks for 70 genetic biomarkers, while the solid tumour sequencing he uses in his hospitals looks at 650, he said.

“The issue is although there are some patients that can’t get their standard markers, I’m still going to want tissue.”

Indeed, Foundation Medicine, which has both solid tumour sequencing tests and now a liquid biopsy test offers a dual-approach.

Foundation’s president and chief operating officer Steve Kafka told Business Insider that tissue biopsies will still be the gold standard, but there is one key area where liquid biopsy could make a major impact.

“What’s exciting about liquid biopsy is — and we think this is going to be an important part of the picture — we believe this will allow physicians to now offer genomic insight to a broader swath of patients for whom tissue is not available,” Kafka said.

For some patients, there’s not enough tissue to get, or they might be too sick to go into a surgical procedure to get the tissue removed.

“Now, rather than being relegated to chemotherapy or guessing, now we have the opportunity to use the liquid biopsy to see if there’s some insight that we can glean.”

But Guardant CEO Helmy Eltoukhy — whose company only has liquid biopsy tests — is convinced the move from solid to liquid will happen.

He said newer versions of the test are already more effective at detecting the mutations than they were two years ago when the test launched and when the study started collecting data.

“In the latest version of the test is that for the major cancer types, like lung and liver cancers, and ovarian cancer, we’re exceeding 90% detection rates in all of those cancer types,” he told Business Insider.

Eltoukhy thinks it’s a matter of time before liquid biopsies are more commonly adopted, comparing the situation to the adoption of wireless phones, where at first it seemed like landlines would still be critical in certain situations, but now cord-cutting is perfectly acceptable.

“The same progression where wireless becomes the primary mode of communication, I do think liquid biopsy will become the primary means of data collection in cancer,” he said.

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