Shining a light on colon testing
Cheap, comfortable screening technique
By Bonnie Kath
Published June 13, 2006
Northwestern University's Vadim Backman has reason to be excited. The assistant professor runs a biomedical optics lab that has been getting phenomenal results in early cancer detection using a technique called enhanced backscattering spectroscopy, or EBS, that he, graduate student Young Kim and their colleagues developed.
With EBS, light sent through a fiberoptic cable shines on human tissue and scatters. About 10 percent of the signal scatters back toward the instrument and is received by sensors and analyzed by computer. That signal contains a wealth of information about the nanoarchitecture of cells, a much more detailed analysis than has ever been possible. In that analysis, it has been discovered that precancerous activity in one area of the body can be spotted in nearby areas, called a "field effect." That has been the focus of the Backman team's work.
"Colon cancer is the second major cause of cancer deaths in the United States," he said. Although the colonoscopy is an effective diagnostic tool, he noted that 60 million Americans in the over-50 age group should be tested annually and that each test costs at least $1,000. No health-care system could pay for all that. Also, patients without symptoms are reluctant to go through the bowel preparation required for the test. "So," he added, "you have about 150,000 deaths per year from colon cancer" in this country.
Backman saw EBS as a way to provide a relatively cheap, non-invasive, comfortable screen that could do for colon cancer patients what the pap smear has done in drastically reducing deaths from cervical cancer. He found that by examining cells in the rectum, he could accurately predict if the colon had polyps, the kind of precancerous tissue the colonoscopist looks for.
When tests on rats and mice yielded promising results, he and Dr. Hemant Roy of Evanston Northwestern Healthcare's Gastroenterology Division recruited 350 people from among patients getting colonoscopies. Each patient was tested with EBS and then the colonoscopy. EBS identified all 43 patients who had the suspect polyps, or adenomatous polyps, in their colons.
It also flagged another 53 patients in whom no polyps could be found during the colonoscopy. These false positives don't bother Backman. It just means that such a patient would go in for the more invasive colonoscopy. "And there are always patients who are developing adenomas [benign tumors] but may not have ... lesions at the time of the colonoscopy."
EBS is geared to be more sensitive to false negatives because if "you tell a [sick] patient he is healthy, he doesn't do any screening, he doesn't do a colonoscopy, and then he dies from colon cancer."
The National Institutes of Health are funding two large-scale studies on EBS, and the data continue to be very strong.
Adam Wax, assistant professor in the Department of Biomedical Engineering at Duke University, is impressed with this new method: "They've shown that EBS can detect cancer much earlier than is possible with any existing technique. I think this technique has the potential to drastically alter the way colon cancer is detected in the clinic."
Backman's group also is trying to tackle pancreatic cancer, examining cells in the nearby duodenum rather than disturbing the pancreatic duct, which contains toxic juices. They have completed a study with 51 patients who were having upper endoscopies, a procedure that sends a scope in through the mouth and down the esophagus, through the stomach and into the duodenum. EBS identified 95 percent of the patients who had pancreatic cancer without ever touching the pancreas.
According to Dr. Michael Goldberg, head of gastroenterology at ENH and a participating physician in these studies, "A number of companies have expressed interest in acquiring this technology. ... Other researchers at major universities have expressed a willingness to test this novel technology, and our hope is to do multicenter studies in the near future and within five years bring this technology to our patients."
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