Now, researchers at University of Missouri (Columbia, MO) have developed a photoacoustic device that can detect individual metastasized melanoma cells in the blood, far sooner than can be seen using imaging equipment and before the cells take root in organs and form into tumours. The system can also capture any detected cancer cells for further analysis.
"This is a blood test that melanoma patients will have, after removal of the primary lesion, in order to detect and track metastatic disease," explained the device's inventor John Viator, associate professor in the University's Bond Life Sciences Center. "It will provide evidence of metastasis months or even years prior to evidence in a conventional CT, MRI or PET scan."
Cell detection
The first step in the test is separation of the patient's blood sample into white and red blood cells. Any circulating tumour cells (CTCs) cells will remain mixed with the white blood cells. This mixture is then flowed through a glass detection chamber. Rather than a continuous flow of cells, the system uses a two-phase flow, in which microlitre droplets of blood cell suspension are separated by similar sized bubbles of air.
Once a droplet enters the detection chamber, it is irradiated by a short pulse of high-intensity laser light. Any cells containing pigment (i.e., the melanoma cells) will absorb the light, heat up and expand, resulting in the emission of a high-frequency acoustic wave. Droplets that emit such signals are diverted for collection and analysis, while those that do not are discarded.
"Of course, positive droplets will contain many normal blood cells, so if purification is necessary, the droplet will be diluted and run through the system again," explained Viator. "One or more passes will result in a purified droplet containing only the CTC and saline."
Captured cells can be individually tested to identify the form of cancer and help choose the best treatment approach for that particular melanoma type. The photoacoustic blood test can also be used to monitor a patient's response to a treatment, tracking whether CTCs increase or decrease over time. This targeted approach could prove of particular benefit as new melanoma drugs enter the market.
Commercial take
Viator has recently signed a license to commercialize his device for research applications, via a newly formed company, Viator Technologies. The research team is also preparing studies for FDA approval, a process that is expected to take two to three years. "Clinical trials will commence after validation and pilot work being conducted this year," Viator told medicalphysicsweb.
The final photoacoustic device will be of similar size to a desktop printer and cost around $100,000. The cost to run each test in a hospital will be a few hundred dollars. Ultimately, the research team hope to adapt the device for detection of other cell types, such as breast, prostate or lung cancer cells.
"We are attempting to provide a faster and cheaper screening method, which is ultimately better for the patient and the physician," said Viator. "There are several melanoma drugs on the horizon. Combined with the new photoacoustic detection method, physicians will be able to use targeted therapies and personalized treatments, changing the medical management of this aggressive cancer. Plus, if the test is as accurate as we believe it will be, our device could be used as a standard screening in targeted populations."