A new method for detecting prostate cancer could eliminate the need for inefficient protein specific antigen (PSA) tests, which have been used for decades as the primary way to screen for the disease.
New research from the Guangdong Medical College in China suggests a laser-based approach could be the latest breakthrough in prostate cancer detection. The non-invasive blood test uses a combination of two techniques: an existing spectroscopy technique called surface-enhanced Raman scattering (SERS) and a new analysis technique called support vector machine (SVM). Together, these scans produce a detection rate carrying a 98.1 percent accuracy — a far cry from the relative guesswork of PSA tests.
"Compared to traditional screening methods, this method has the advantages of being non-invasive, highly sensitive, and very simple for prostate cancer screening,” said study leader Shaoxin Li in a statement.
Traditional PSA tests actually do a good job of screening for prostate cancer — known in medical parlance as carrying “high sensitivity.” Unfortunately, they’re also good at detecting non-threats, known as false-positives, which means they come with “low specificity.” The challenge for cancer researchers is finding a test that can match PSA tests’ sensitivity to cancer, but at the same time ignore all the unnecessary noise. According to the Centers for Disease Control and Prevention, prostate cancer is the most common cancer among men in the U.S.
After collecting blood samples from 68 healthy volunteers and 93 people who were confirmed to have prostate cancer, the experimenters ran the SERS imaging, This process relies on a phenomenon known as Raman scattering, in which the light that shines on a particular substance reveals its chemical composition. In prior uses, Raman scattering revealed the presence of brain tumors among healthy tissue. In the latest study, the team then fed each of these scans through an algorithm that detected even the subtlest changes.
Li and his colleagues say their research was born out of a recent announcement from the U.S. Preventive Task Force warning against the use of PSA tests, specifically because they carry such a high risk for misdiagnosis. In addition, science has been sitting on the Raman scattering-based technique for years, but people were afraid of using it because the changes it picked up were too subtle. That’s where SVM came in. With a powerful new analysis tool, the team was able to measure tiny differences that otherwise would have flown under the radar.
These findings upheld SERS as a viable alternative to PSA tests. Up next are clinical trials, the researchers say. Now that they’ve got the proof-of-concept under their belt, Li and his team hope to see how much specificity the technique can achieve. For instance, in upcoming studies they’ll screen for prostate cancer in multiple stages, checking to see whether SERS is able to detect the cancer across all stages of development or simply toward the end, after it has metastasized.
What remains unclear is whether the new SERS-based test will be able to replace the traditional rectal exam administered to middle-aged men around their 40th birthday. Typically, doctors perform rectal exams because they have the benefit of quick, minimally invasive assessment. In years past, if a doctor felt cause for concern, he or she would order a PSA test, which could lead to painful biopsies. If the new blood test emerges as a clinical alternative, the dreaded gloved finger could join countless other procedures as relics of medical science.
Source: Li S, Zhang Y, Xu J, et al. Noninvasive prostate cancer screening based on serum surface-enhanced Raman spectroscopy and support vector machine. Applied Physics Letters. 2014.