Diagnostics & Imaging Week Washington Editor
WASHINGTON — The prevalence of colon cancer has become more conspicuous on the nation’s healthcare radar screen because the disease is so disabling, leading to lost time at work, and so expensive to treat. And several studies fleshed out, at a press conference during this year’s Digestive Disease Week 2007 gathering, some of the more difficult issues in detecting and treating this disease.
Moderating the session was Don Rockey, MD, the director of the liver center at Duke University Medical Center (Durham, North Carolina). Rockey said that “colon cancer is the second-leading cause of cancer-related mortality” in the U.S., citing two important issues in dealing with this disease: “diagnosis and the quality” of diagnosis, given the difficulty of finding every polyp inside the labyrinthine human colon.
Roy Soetikno, MD, an assistant professor of gastroenterology at Stanford University School of Medicine (Palo Alto, California), reviewed a study he co-authored to evaluate whether wide-angle view colonoscopy — which typically captures a field of about 170 degrees and employs a source of light known as narrow-band imaging — compared favorably with the standard electronic scope offering a 140-degree view and employing white light.
However, to even the playing field, the researchers used only scopes with a field of 170 degrees, the source of light as the only variation between the two devices in the study.
Soetikno said that about 150,000 Americans will be diagnosed with colon cancer in 2007, and that “up to 90% of these cancer deaths may have been preventable.”
He said that colonoscopy is “the gold standard to find these lesions, although it has been shown that it is not perfect,” referencing a missed diagnosis rate of from 22% to 24% employing ‘scopes developed a decade ago.
Narrow-band imaging, said Soetikno, “comes with the ability to perform contrasts,” depicting lesions in a brownish color and surrounding normal tissues in a greenish hue. The researchers examined whether this color differentiation would aid diagnosis. Enrolling about 142 patients each in the control and study arm, the authors found that “our adenoma miss rate on both arms was about equal,” at about 12[%] to 13%, and almost all the missed adenomas were smaller than one cm.
“We showed that our detection rate is quite high” compared to traditional colonoscopy, Soetikno said, but “NBI did not reduce the miss rate and did not improve the detection rate.” He added that any trials to evaluate CT colonography should be compared against new endoscope technology, pointing out that the 24% miss rate “was reported in 1997 and is not a very good benchmark.”
However, given the better detection rates offered by modern electronic colonoscopy, “I hope we will all be moving toward the new technology,” Soetikno said.
Many gastroenterologists are reluctant to perform an invasive procedure like a colonoscopy on their elderly patients for fear of compromising the patient’s health, with perforation of the colon one of the prime concerns. However, a study presented by Kinesh Patel, MB, a senior house officer at Hammersmith Hospital (London) suggested that these concerns might be overblown.
However, Patel said that while colonoscopy is “safe in this population, it is often more technically challenging due to difficulties with adequate bowel preparation and the safe administration of sedation.”
In a study of nearly 1,900 colonoscopies, more than 1,500 were performed on patients over the age of 75, the results suggesting that the elderly might think that their younger counterparts are a bunch of lightweights.
While slightly less than 12% of the procedures on the under-75 crowd were terminated and almost 21% on the older patients were cut short, the reason for this disparity is not that the older patients complained. Patel said the main reason was “poor bowel preparation.”
Contrary to popular belief,” Patel said, “aborted examinations due to discomfort in the elderly are rare.”
His numbers indicated that roughly 42% of those examinations were stopped due to poor preparation, and less than 1% stopped because the patient complained.
In the younger population, 2.6% were terminated due to discomfort. Patel said, “these data show that the elderly tolerate colonoscopy better than younger patients.”
Still, he suggested that the phenomenon be studied further because this is a fairly vulnerable population. “There are risks of course, but generally, its been shown to be pretty safe.” He cited airway disease and profound heart disease as risk factors for colonoscopies among the elderly.
C-reactive protein (CRP) has fallen back into the ranks as a biomarker of inflammation-related heart disease, but it may find a role in diagnosis of colorectal cancer.
Addressing an association between elevated CRP and colorectal adenomas, Han-Mo Chiu, MD, a lecturer at the National Taiwan University Hospital (NTUH; Taipei), discussed a “simple association study” aimed at establishing whether previous reports of a link between CRP and colorectal adenomas were valid and whether this association varied by the sex of the patient. Adenomas are widely seen as the primary morphological precursor to these cancers.
Plasma levels,” said Chiu, “were significantly higher in subjects with colorectal neoplasia than those without” by a margin of 1.84 milligrams per liter (mg/L) to 1.47 mg/L, but he noted that “gender stratification showed positive association ... in men, but no corresponding association was noted in women.”
Chiu said that differences in fat composition between men and women might be behind the difference in CRP readings. He also noted that larger polyps were associated with higher levels of CRP, as were cancerous cases versus non-metastatic polyps.