Cancer cells are sometimes known to break off from a tumor and travel through a person’s bloodstream, and finding those cells can help doctors predict whether more tumors will develop elsewhere in the patient’s body. But these cells also incredibly difficult to locate, because there are so few of them: while a one milliliter sample of blood contains about five billion red blood cells, it would only contain about ten of "circulating tumor cells," or CTCs.
But in a study published this week in PNAS, scientists say they have developed a new method to distinguish the cancerous cells from the healthy ones, with a device that separates the cells out using sound waves.
Popular Science explains how it works:
The device consists of two acoustic transducers on either side of a very small channel. The wave-producing transducers are angled in a way that they create a "standing wave," which has sections of high and low pressure. When the researchers place a blood sample in the channel, the standing wave pushes cells to either side of the channel. The peaks and troughs of pressure end up separating the cancerous cells from the regular, healthy cells, due to the CTCs' varying shape and compressibility. The researchers ran the experiment on a sample with two types of CTCs of similar size and found that the device successfully separated out 83 percent of the cancerous cells.
While other methods to find CTCs do currently exist, they rely on antibodies to bind to the cancer cells—so doctors need to already know what type of cancer it is before they do the test, in order to know which antibodies to use. The researchers explain the new instrument is a breakthrough improvement that could be used to determine the presence of cancer at any stage. Plus, unlike current methods, the device does not damage the cells in the process of finding them, which would make it easier for doctors to pinpoint the most effective treatment.