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Non-invasive blood test for colon cancer could improve screening procedures


Researchers from BC Cancer Agency and the University of British Columbia (both Canada) have discovered a method to screen blood samples for molecular traces that indicate the presence of precancerous polyps in the colon, a significant warning sign for colon cancer. Their findings, recently published in Biomedical Optics Express, could lead to a cheaper and less invasive initial screening test for colon cancer to complement colonoscopy.

Current screening technologies, such as colonoscopy, usually lead to the detection of colon cancer in its earliest stages. Colonoscopy is, however, invasive, unpleasant and can be expensive. Patients must drink large volumes of laxatives before the procedure, and sedation or anesthesia is required during the exam.

Current guidelines recommend that adults 50 years and older should have a colonoscopy every 10 years, or sooner or more frequently if other risk factors exit. However, US Centers for Disease Control and Prevention statistics say that only 65% of American adults actually follow these guidelines.

Many researchers are therefore searching for less invasive alternatives to colonoscopy that may encourage more people to get tested.

In an attempt to develop an alternative, cheaper and less invasive test, researchers from BC Cancer Agency and the University of British Columbia identified differences in the blood of people with precancerous polyps compared to people without such polyps.

The team collected plasma samples from three groups of individuals: 23 who possessed precancerous polyps, 21 who had verified colon cancer and 25 healthy volunteers. Plasma from each individual was mixed with silver nanoparticles and then analyzed using surface-enhanced Raman spectroscopy.

In earlier work, collaborators from Fujian Normal University (China) demonstrated that there is a difference in the Raman spectra of the blood plasma of people with colon cancer compared to cancer-free individuals. This new study showed that the test can also be used to identify people with precancerous polyps — this could mean the technique is even more useful for a screening test, since it may be able to identify cancer risk before the disease actually develops.

Initial results are promising, but the procedure is still in the research phase and additional laboratory tests and clinical trials are needed before the test can be implemented. The team needs to determine the exact bimolecular source for the difference in blood samples. “We are planning new research to identify these responsible molecules,” commented Haishan Zeng (BC Cancer Agency), the study leader.

It is also important to note that a blood test for colon cancer will never fully replace colonoscopy. Once polyps are identified, a colonoscopy is still the best way to find out where they are located in order to remove them. This being said, a blood test could be used as a first line of defense to identify individuals with warning signs of cancer. High risk individuals could then be referred for a colonoscopy.

Sources: New blood test for colon cancer improves colonoscopy screening results; Feng S, Wang W, Tai I, Chen R, Zeng H. Label-free surface-enhanced Raman spectroscopy for detection of colorectal cancer and precursor lesions using blood plasma. Biomedical Optics Express 6(9), 3494–3502 (2015).


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