THE OPTICAL
SOCIETY
Optical Raman
Spectra of Blood Shows Simple Fingerprint for Cancerous Growth and Precancerous
Polyps
August 24th, 2015
IMAGE: A NOVEL
TEST SHOWS A DIFFERENCE IN THE RAMAN SPECTRA OF THE BLOOD PLASMA OF PEOPLE
WITHOUT COLON CANCER COMPARED TO THOSE WITH PRECANCEROUS OR CANCEROUS POLYPS.
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CREDIT: HAISHAN
ZENG, BC CANCER AGENCY
WASHINGTON --
Canadian researchers have found a way to screen blood samples for molecular
traces that indicate the presence of precancerous polyps in the colon, a key
warning sign for colon cancer. Their results, published this week in the
journal Biomedical Optics Express, from The Optical Society (OSA), may yield a
cheaper and less invasive initial screening test for colon cancer that could
complement colonoscopy, though further clinical trials will need to demonstrate
the safety and effectiveness of the blood test before it is routinely used.
"This is a
screening technology you can use on anybody," said Haishan Zeng, BC Cancer
Agency, who led the study.
Thanks in part
to screening technologies like colonoscopy; colon cancer is often detected in
its earliest stages. By snaking a camera through a patient's intestines,
doctors can identify polyps and other abnormal growths that could eventually
become cancerous then remove them before they do. Many lives are saved each
year because of this sort of routine screening.
The procedure
can also be expensive and unpleasant. Patients must drink large quantities of
laxatives the night before and undergo sedation or anesthesia during the exam
itself. Current health guidelines say that adults should have a colonoscopy
every ten years beginning at age 50 -- and sooner or more frequently if other
risk factors exist -- but U.S. Centers for Disease Control and Prevention (CDC)
statistics say that only 65 percent of American adults actually follow these
guidelines.
That's why many
researchers are searching for less invasive alternatives to the colonoscopy
that could induce encourage more people to get tested.
In a step
towards this goal, researchers from the BC Cancer Agency and the University of
British Columbia have identified differences in the blood of people with
precancerous polyps compared to people without such polyps. Their results could
eventually lead to a cheaper and less invasive initial screening test for colon
cancer.
The team
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).
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.
In previous
work, the team's collaborators at Fujian Normal University showed a difference
in the Raman spectra of the blood plasma of people with colon cancer compared
to individuals who were cancer-free. This new study demonstrated that the test
can also be used to identify people with precancerous polyps -- a finding that
makes it potentially more useful for a screening test, since it may be able to
identify cancer risk before the disease actually develops.
A blood test
that could detect precancerous polyps would be an improvement over other
non-invasive colon cancer screening mechanisms currently available. For
instance, the fecal occult blood test is an at-home kit that looks for evidence
of microscopic traces of blood in stool samples, a potential sign of cancer.
However, many early-stage colon cancers are asymptomatic and don't bleed,
leaving them undetectable by this measure.
The initial
results are promising, but the procedure is still in the research phase and
must go through additional lab tests and clinical trials before actually being
implemented. For instance, although the team identified significant spectral
differences between the blood samples, they haven't yet determined the exact
biomolecular sources for these differences. "We are planning new research
to identify these responsible molecules," said Zeng.
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're 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; these high-risk
patients could then be referred for a colonoscopy to learn more.
###
Paper: S. Feng,
W. Wang, I. Tai, R. Chen, H. Zeng. "Label-free surface-enhanced Raman
spectroscopy for detection of colorectal cancer and precursor lesions using
blood plasma," Biomedical Optics Express 6, 3494-3502 (2015).
About Biomedical
Optics Express
Biomedical
Optics Express is OSA's principal outlet for serving the biomedical optics
community with rapid, open-access, peer-reviewed papers related to optics,
photonics and imaging in the life sciences. The journal scope encompasses
theoretical modeling and simulations, technology development, and biomedical
studies and clinical applications. It is published by The Optical Society and
edited by Joseph A. Izatt of Duke University. Biomedical Optics Express is an
open-access journal and is available at no cost to readers online at: OSA
Publishing.
About The Optical Society
Founded in 1916,
The Optical Society (OSA) is the leading professional organization for
scientists, engineers, students and entrepreneurs who fuel discoveries, shape
real-life applications and accelerate achievements in the science of light.
Through world-renowned publications, meetings and membership initiatives, OSA
provides quality research, inspired interactions and dedicated resources for
its extensive global network of optics and photonics experts. OSA is a founding
partner of the National Photonics Initiative and the 2015 International Year of
Light. For more information, visit:
http://www.osa.org.
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