Novel Blood Test for Colon Cancer Improves Colonoscopy Screening

Surface enhanced Raman spectroscopy (SERS) using silver nanoparticles as substrate is a multiplexed analytical technique capable of detecting biomolecules with high sensitivity.

The use of SERS to screen blood samples for molecular traces that indicate the presence of precancerous polyps in the colon, a key warning sign for colon cancer, has been demonstrated and may yield a cheaper and less invasive initial screening test for colon cancer that could complement colonoscopy.

Scientists at the BC Cancer Agency (Vancouver, BC, Canada) and their colleagues, collected blood plasma samples from three groups of people: 23 who had adenomatous (precancerous) polyps, 21 who had verified colon cancer, and 25 healthy volunteers. They mixed each plasma sample with silver nanoparticles and then analyzed the mixtures with surface-enhanced Raman spectroscopy (SERS).

A fully integrated fiber optic probe real-time Raman spectrometer (Aura, Verisante Technology Inc., Vancouver, Canada) was used to take the SERS spectra. The 785 nm excitation laser generates 150 mW output power at the fiber optic probe tip. Raman spectroscopy uses a laser to excite the sample and measure shifts in the vibrational energy of its molecules, which can provide insight into the sample's molecular structure. In surface-enhanced Raman spectroscopy, nanoparticles are added to boost the signal. Partial least squares discriminant analysis (PLS-DA) with leave-one-out cross validation was used to generate classification models. For colorectal cancer (CRC) and polyp detection diagnostic, a sensitivity of 86.4% and a specificity of 80.0% were achieved.

The authors concluded that the use of surface-enhanced Raman spectroscopy based blood plasma analysis as a noninvasive, accurate, and convenient alternative screening test for detecting both CRC and polyps is feasible. Although a blood test for colon cancer will never replace colonoscopy: once polyps are identified, a colonoscopy is still the best way to figure out where they are located so that they can be removed. However, a blood test could be used as a first line of defense to identify patients with warning signs of cancer and these high-risk patients could then be referred for a colonoscopy for a more definitive diagnosis. The study was published on August 24, 2015, in the journal Biomedical Optics Express.

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BC Cancer Agency
Verisante Technology Inc.