NNMC Study Finds Colonoscopy Most Effective Method of Colon Cancer Screening
Story Number: NNS050602-08
Release Date: 6/3/2005 3:00:00 AM
By Ellen Maurer, National Naval Medical Center Public Affairs
BETHESDA, Md. (NNS) -- Colon cancer experts from the National Naval Medical Center (NNMC) participated in a collaborative study with the National Cancer Institute that found colonoscopy detects cancer better than other screening methods in women.
According to the yielded research, which was published in the New England Journal of Medicine May 19, other common screening methods such as fecal blood testing and flexible sigmoidoscopy (examining only the lower quarter of the colon) are not as successful in diagnosing advanced pre-cancerous polyps. In fact, screening methods other than colonoscopy may end up missing deep-set pre-cancerous colon polyps in up to 30 percent of men and up to 65 percent of women, according to the study’s lead author, Phillip Schoenfeld. Formerly of NNMC and now an assistant professor at the University of Michigan Medical School, Schoenfeld continues to work with the Gastroenterology division at NNMC and the Uniformed Services University of the Health Sciences.
“While fecal occult blood testing and flexible sigmoidoscopy are less expensive, faster and require no sedation, 65 percent of women with advanced pre-cancerous polyps in our study would have lesions missed if these were the only screening tests performed, because pre-cancerous polyps are found deeper in the colon in women,” Schoenfeld said in an interview with the Newswise media agency.
The study’s findings may be most significant for the civilian health care industry. NNMC has used colonoscopy as its primary screening tool since 2001, but many civilian providers are still using blood testing and sigmoidoscopy, according to Cmdr. Brooks Cash, director of Clinical Research within the Gastroenterology Division and Colon Cancer Center Initiative at NNMC.
“Many places in the country do not have the necessary resources to offer colonoscopy to all eligible patients,” Cash said. “That being said, sigmoidoscopy and stool cards are acceptable methods of screening; some screening is better than no screening at all.”
The study not only reaffirmed the value of colon cancer screening, it also exposed some slight differences between the way men and women develop colon cancer. The study – first of its kind to focus on female patients – also seemed to indicate women tend to develop colon cancer 10 to 12 years later in life compared to men; however, experts feel this may have little impact on overall disease progression.
“It does appear from our data that women may have a tendency to develop proximal colon cancer more than men, but we need additional studies to confirm this observation," Cash said. "The important point to make from both of these studies is that a flexible sigmoidoscopy, which involves examining only the distal colon, does not appear to be as effective as total colonic examination with colonoscopy, because of the frequency of advanced lesions that would otherwise be missed.”
According to Cash, both sexes have the same statistical chance of developing colon cancer, and about 6 percent of those who are not screened regularly develop colon cancer. Therefore, Cash said regular screenings are vital to survival.
“Regardless of gender, survival is directly related to the stage of the disease when it is identified. Evidence shows that screening for colon cancer leads to both prevention of cancer by removal of polyps and identification at an earlier stage if cancer is already present,” Cash said.
With screening for colon cancer being the known key to survival, Cash and his team at NNMC are also exploring the value of new technology that allows doctors to view the colon through a less invasive procedure. It is called virtual colonoscopy, and the procedure uses X-rays and computers to produce two- and three-dimensional images of the colon and rectum. They hope that this technique will allow them to provide screening for up to 15,000 people per year, more than three times what they can provide with traditional colonoscopy.
Additionally, NNMC’s Comprehensive Colon Cancer Center Initiative, which officially opens this month, is working with investigators from the National Cancer Institute and various other departments in NNMC to explore other colon cancer related issues. One study hopes to determine whether or not less invasive tests, such as looking for abnormal DNA in stool or abnormal proteins in blood, could be other viable screening tests for colon cancer.
