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Today’s methods of detecting circulating tumor cells (CTCs) in blood are hampered by poor sensitivity, which limits the so-called liquid biopsies’ usefulness for catching low-level CTCs present before metastasis, when prognosis is better. A new photoacoustic liquid biopsy approach that peers through the skin was more sensitive than existing assays in detecting CTCs in patients with melanoma.
Researchers led by Vladimir Zharov, PhD, DSc, of the University of Arkansas for Medical Sciences in Little Rock, described their platform, called the Cytophone, in Science Translational Medicine. Laser pulses delivered to veins through the skin heated the melanin in melanoma cells, producing telltale acoustic waves picked up by an ultrasound transducer.
The method directly detected CTCs in 27 of 28 people with melanoma, with no false-positives in the cancer-free control group. The findings were confirmed with 6 ex vivo methods. In comparison, existing assays can detect circulating tumor cells in less than 40% to 60% of patients with cancer.
The new technique took just 10 to 20 seconds to find tumor cells in the bloodstream of patients with higher CTC concentrations; those with lower levels required 15 to 60 minutes of monitoring. Ultimately, the approach was able to detect as few as 1 CTC per liter of blood, making it up to 1000 times more sensitive than other liquid biopsies, according to the authors.
Different acoustic patterns also identified circulating blood clots, which can block blood vessels and are a major cause of cancer-related death. The technique also appeared to destroy CTCs in some patients, a finding confirmed in vitro.
Abbasi J. Detecting Circulating Tumor Cells Through the Skin. JAMA. 2019;322(6):495. doi:10.1001/jama.2019.11240
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