PHILADELPHIA, March 9 (AScribe News) -- By now, everyone has heard the statistic that 50 percent of marriages will end in divorce. Perhaps a more startling figure is that every married couple has a one in 10 chance that either the husband or wife will develop colon cancer in his or her lifetime.
Dr. Radhika Srinivasan, assistant professor of medicine in the Gastroenterology section at Temple University Hospital, is currently conducting research that she hopes will improve the rates of cancers that are identified and cured through screening. She is studying people being screened for colorectal cancer in order to identify a surrogate marker that might indicate cancer of the bowel earlier for a larger number of patients.
Srinivasan has completed the first phase of her study by collecting samples from patients who exhibit symptoms of colon cancer or polyps and are undergoing colonoscopy. The research is looking to correlate levels of Proliferating Cellular Nuclear Antigen (PCNA), a cellular protein, collected from normal sigmoid mucosa with findings of advanced colonic polyps and cancer in the proximal portion of the colon.
"Our ultimate aim with this study is to develop a surrogate marker from the sigmoid mucosa which will prompt a total colonoscopic examination even in patients with normal sigmoidoscopy," says Srinivasan.
She says that her research has produced encouraging results so far.
"We have seen elevated PCNA levels in the distal colon in symptomatic patients with advanced polyps and cancer farther up in the bowel. If our finding is borne out in average risk patients, this should help physicians to better determine which average risk patients might benefit from further screening for cancer using colonoscopy. If a flexible sigmoidoscopy is negative but PCNA levels are high, it might be wise to recommend total colonoscopic screening," she explains.
Since colorectal cancer rarely causes symptoms in its early stages, proper screening is imperative for anyone over the age of 50 as well as any younger people who have symptoms or risk factors.
Current screening recommendations for average risk patients consist of an annual fecal occult blood test (FOBT) and a flexible sigmoidoscopy every five years for every man and woman over the age of 50. FOBT, a test normally done at home, tests for traces of blood in the stool, one of the symptoms of colon polyps or cancer. A flexible sigmoidoscopy entails a gastroenterologist or internist inserting a thin, lighted telescope in through the lower third of the colon to check for polyps or abnormal growths.
A full colonoscopy is recommended for anyone who is at higher risk for colorectal cancer due to prior history of colonic malignancy or polyps, a strong family history of the disease or a chronic digestive condition like inflammatory bowel disease. It works much like a sigmoidoscopy, but allows the physician to look at the entire large intestine and into the last portion of the small intestine. Both tests allow the gastroenterologist to remove any premalignant polyps while the screening is in progress.
Srinivasan explains that most insurance companies will pay only for flexible sigmoidoscopy for patients with no risk factors for colorectal cancer.
"While flexible sigmoidoscopy is a good gauge for detecting polyps and cancer, it is not perfect. Since the test only looks at the lower third of the bowel, cancer may go undetected if it appears in the farthest portion of the colon. It's comparable to a woman getting a mammogram on only one breast. You will detect some of the cancers some of the time, but will most definitely miss some as well," says Srinivasan.
PCNA levels are measured in a variety of ways. Three different techniques are used to determine PCNA from sigmoid mucosal samples as well as a serum blood test to correlate with the mucosal findings. The results from all measurements are then compared to the results of a colonoscopy.
Ultimately, Srinivasan hopes that a sensitive and specific screening tool can be developed that can prospectively be used to screen asymptomatic patients who are at average risk for developing colon cancer.
She comments, however, that, "Even improved tests can only help those that follow the recommendations and see their doctor to be screened once they turn 50 years of age. Since colorectal cancer can occur without symptoms, we hope that more precise screening will prevent and cure a greater number of cancers."
