Liquid Biopsy, Detecting Cancer DNA Before Tumors

A new blood test is capable of identifying genetic markers for eight major types of cancer. Though it only correctly identified cancer 70% of the time, this so-called “liquid biopsy” is a minimally invasive way to screen for cancer when no symptoms are present. It is at this stage cancer is at its most treatable, and at $500 costs no more than a colonoscopy, mammogram, or other cancer screenings.


The importance of such a test cannot be overstated in the fight against cancer. Insidious cancer cells can essentially lie dormant for 20-30 years before they grow into large, spread out masses that are difficult or impossible to eradicate. By identifying the cancer in its nascent stages, it can be usually be readily cured using radiation, surgery, or other common treatments. The difficulty lies in identifying the cancer DNA in patients blood, which is often present in miniscule amounts, and even when identified it can be difficult to trace the tissue of origin.

The eight major cancer types being screened here account for 60%, or 360,000, of all cancer deaths in the US last year, and there is nothing more critical to their effective treatment than an early diagnosis. Though as you can see from the accompanying chart, detectability varies; but this methodology is a work in process with large-scale human trials set to begin soon.

The research comes out of Johns Hopkins University in Baltimore and has been published in the journal Science. As this research begins large-scale human trials it will be evaluated for its utility in hospitals and doctors offices. The hope is that the principles underlying this methodology can be expanded to identify more types of cancer, and with greater accuracy. We may never be able to cure late stage cancer, and the treatments are often ghastly; but if the disease can be identified before it even forms tumors, the cancer can very likely be cured.


Cohen JD, Li L, Wang Y, Thoburn C, Afsari B, et. al. (2018) Detection and localization of surgically resectable cancers with a multi-analyte blood test. Science. 359(6378): 926-930


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