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New Alternative for Colonoscopy

Ask anyone who has had a colonoscopy, and the answer is the same: it's no fun. With a day of dietary restrictions and bowel prep, followed by sedation for the procedure and an uncomfortable recovery, it's no surprise that only 15 percent of Americans who should get a colonoscopy actually do. That low number contributes to colon cancer's status as the second leading cause of cancer death for both men and women — particularly disturbing given the success rate of early detection and treatment.

"Many people don't realize it, but we aren't winning the battle against colon cancer," says Vadim Backman, professor of biomedical engineering. Backman aims to make a big impact on colon cancer detection by changing the way medical practitioners screen for the disease.

A novel alternative screening procedure developed by Backman and being tested in collaboration with Hemant Roy, associate professor of medicine at Northwestern's Feinberg School of Medicine and director of basic and clinical research for the gastroenterology section at Evanston Northwestern Healthcare, is a step closer to widespread use by medical practitioners.

As described in the spring 2005 issue of By Design, the procedure uses optical technology to screen the base of the colon for precancerous changes. Knowing that small changes occur in the entire organ when precancerous polyps develop at any point of the colon (a phenomenon called "the field effect"), Backman's research team designed a 1 millimeter probe that can be inserted at the base of the rectum to detect small cellular changes that can signal cancer. The test can completely replace the traditional colonoscopy for patients who show no signs of polyps.

When By Design reported on Backman's work in 2005, the test using a technique called four-dimensional elastic light-scattering fingerprints (4D-ELF) showed great promise. A new breakthrough has given the research team even better results recently. Backman and then-graduate student Young Kim, PhD '05, were the first to observe low-coherence enhanced backscattering (LEBS) in tissue. Although LEBS had been well documented on hard media, it was previously thought of limited value for obtaining data from weakly scattering media such as tissue. Backman's discovery opened the door to new tests with increased sensitivity.

"We can use this technology to derive information about the nanoscale architecture of tissue," Backman says. "This technique actually allows you to probe the nanoarchitecture of cells, which was previously impossible."

Clinical success

Over the past year Backman has worked with Roy at Evanston Northwestern Hospital to implement clinical trials for the technology. Testing the procedure with patients already undergoing a colonoscopy, the team compares its results with those of the gastroenterologist. So far tests with more than 500 patients have yielded impressive results.

The studies have shown a perfect rate of identifying individuals with no polyps in the colon. "When I first saw the results, I thought they were too good to be true," Backman remarks. "Not a single patient who has tested positive in the colonoscopy has tested negative with our screening."

When the test indicates that someone may have a polyp, it is right about 70 percent of the time. But those false positives aren't a major concern to Backman and Roy, because such a patient would undergo a colonoscopy for further examination. "While it is important to find a relatively noninvasive way to say that someone has a polyp, it's even more important to find a noninvasive way to say that they don't have a polyp," Roy says.

Colonoscopies are recommended every 10 years for people over age 50. As the population of Americans who should have colonoscopies grows — the number is about 75 million now — it's become impossible for everyone who needs a colonoscopy to actually get one. If everyone received a test every 10 years, the annual cost would rise to $10 billion, and gastroenterologists would not be able to meet the demand. Clinics are already nearing their capacity with only 15 percent of eligible Americans undergoing the procedure.

Expanding the research

As a physician, Roy appreciates Backman's thoughtful approach to finding a clinically relevant application for his work. He explains that almost everyone working in biomedical optics for colon cancer has been working on an optical biopsy for use during a colonoscopy to determine if a polyp needs to be removed.

"It's important work, but from a practical point of view, I don't know if it helps me take care of my patients," Roy says. Because doctors know that 90 percent of polyps are removed, standard practice today is to remove all polyps without determining if they are cancerous.

"Vadim's work is a paradigm shift," Roy says. "We don't just want to know what the pathologist can tell us tomorrow; we want to address the major clinical issue by getting the right people screened. Then we can use our endoscopic capacity to make a real dent in colon cancer mortality."

Backman and Roy have secured funding from the National Institutes of Health to run clinical trials for 3,000 patients over the next three years. They're also working to expand their study to other medical research centers. If the data continue to be as promising as the initial results, the team will apply for FDA approval and pursue options for widespread distribution. Ideally, the technology would be used by a primary care physician to determine if a patient needs a colonoscopy.

In the meantime, Backman is working to apply his techniques to other kinds of cancer. He recently received a grant from the V Foundation for Cancer Research to apply the technology to pancreatic cancer and is in the preliminary stages of applying it to lung cancer.

In addition to clinical trials, Backman hopes to gain an understanding of the field effect on which his screening techniques are based. Little is understood about why all cells in and around an organ change if cancer is present.

"If you want to save lives, it's not important that you understand the biological and molecular mechanisms behind this technology," he explains. "But if you figure them out, perhaps it could lead to an understanding of cancer or the discovery of new therapies."

Source hxxp://bydesign.mccormick.northwestern.edu/FA2006/Backman.html


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