Noninvasive laser detects, kills melanoma cells in bloodstream

Zharov said the test is 1,000 times more sensitive than existing techniques, which usually rely on much smaller amounts of blood from blood tests. Seeking a solution, Ekaterina Galanzha and colleagues created a system called the Cytophone that uses laser pulses and focused ultrasound to noninvasively peer under the skin of patients with melanoma, revealing pigmented CTCs that pass through veins in the arm. ("Cyto" means cell.) When they shine the Cytophone's laser on an animal's or person's skin so that its light penetrates a few millimeters into near-surface blood vessels, any passing melanoma cells slightly heat up due to their dark pigment, melanin. This harmless heating creates a tiny acoustic wave that gets picked up by the ultrasound detector. The device correctly identified all 19 healthy patients, and detected CTCs in 27 of 28 melanoma patients. In the latter group, CTCs were detected in as little as 10 seconds. An average blood sample taken from a patient consists of only a few mL, which may or may not contain any CTCs.

The Cytophone uses photoacoustic flow cytometry to scan a patient's entire blood supply for CTCs, which are often sparse and hard to detect, with the ability to identify even just one CTC per liter of blood, a detection rate approximately 1,000 times more sensitive than existing methods. Importantly, the system's laser could destroy the detected CTCs, resulting in a large drop in CTC numbers. It could also be used as an add-on to skin checks to improve screening for melanoma, like a mammogram for breast cancer, he suggests.

The treatment could allow doctors to quickly scan patients' blood without ever removing it from them, to spot circulating tumour cells or CTCs, which can go on to spread around the body and become the deadly metastases that often kill people with cancer, The Independent reports.

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The Cytophone also has shown the ability to detect CTCs even when the tumor is not identifiable on the skin, either because too small (known as the T0 or TX stage) or after surgical removal, and then to destroy them without harming surrounding blood cells.

Other applications for the Cytophone in label-free mode could include detection of sickle cells to prevent sickle cell crisis, detection of clots to prevent stroke, and selection of the most effective drug through monitoring of circulating disease-associated markers count decrease. For now, she says, "It is a very cool study with lots of promise".

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