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Wednesday, April 25, 2018

Research

New liquid biopsy technique looks for both gene mutations and tumor-related proteins

It is likely that one day a single blood test can be used to detect a variety of cancers. In the last few years a variety of tests called liquid biopsies have been developed that hold the hope of detecting and tracking tumors from a simple blood draw. Many of the tests detect tumor-associated DNA mutations. But detecting scant DNA released by early stage tumors is daunting. Furthermore, false positives are a constant concern.  In an online post in the journal Science (Cohen et al , Science), researchers and collaborators at Johns Hopkins reported on a newly developed test dubbed CancerSEEK. The test examined the levels of 8 tumor-related proteins and the presence of mutations in 16 genes often mutated in various cancers. The researchers tested this liquid biopsy on 1005 patients diagnosed with non-metastatic cancers of the ovary, liver, stomach, pancreas, esophagus, colo-rectum, lung and breast. The accuracy of CancerSEEK varied depending on the cancer: it detected 98% of ovarian cancers but only 33% of breast cancers. However, in looking at the entire cohort, the sensitivity was 69% or higher for cancers of the ovary, liver, stomach, pancreas and esophagus. The false positive rate in 812 healthy patients was <1%. One caveat is that the cancer-related proteins can also appear in people with inflammatory diseases such as arthritis and may increase the false positive rate in this population.

A study of CancerSEEK is now underway in the Geisinger Health System in Pennsylvania on female volunteers between ages of 65 and 75 who have never had cancer. The study is being done in collaboration with Johns Hopkins. For those patients who test positive twice, imaging will be used to attempt to find a primary tumor.

“If people expect to suddenly catch all cancers, they’ll be disappointed,” says cancer researcher Nitzan Rosenfeld of the University of Cambridge in the United Kingdom. “This is exciting progress,” he says. “But evaluating it in the real world will be a long process.”

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  • 33% sensitivity for breast cancer is dismal, but the results managed to squeeze into this article by virtue of the better results with other types of cancer. While “liquid biopsy” is a relatively new term (originally applied to tumor DNA fragments, but now to any blood test for cancer), the research is not new. Over the past 20 years, I’ve sent out 10,000 samples to researchers around the world, working on this challenge. Several proposed uses, including helping radiologists when imaging findings are ambiguous, monitoring for recurrence, etc., but my interest is in women with normal mammograms (or those who refuse mammography, or are too young for mammography) for whom US or MRI could be done if mammos negative, but blood test positive. Multiple groups are close to having something useable, with sensitivity 80-85% and specificity 80-85%. Importantly, results seem to work independent of breast density, so by the time you get to Level D density, currently available technology would likely find more cancers than mammography. GRAIL study has many in this space excited, but quite a few biotechs have blood tests under study that could be available before anything comes of GRAIL. Blood testing has even greater potential if it would detect only those cancers that are biologically important (as first proposed by Dr. L. Esserman), so it may turn out that we don’t end up with a “general” blood test, but with a Luminal B result, triple-negative result, HER2+ result, etc., a “panel” so to speak. For right now, just trying to hit 90/90 Sens/Spec.

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