Colonoscopy Remains the Gold Standard to Detect Colon Cancer

< Mar. 11, 2009 > -- Medical experts say you can still trust a colonoscopy to detect and prevent colon cancer in its earliest stages, even though recent research has pointed out some potential drawbacks in having this procedure.

"Colonoscopy is a good tool," says Dr. Durado Brooks, national director of prostate and colorectal cancers for the American Cancer Society (ACS). "In the right hands, it is an effective tool. But we have known for a long time it is not a perfect tool."

In December, 2008, Canadian researchers reported that colonoscopies were good at discovering early signs of cancer on the left side of the colon, or large intestine, but were not as good at finding cancer or polyps on the right side, deeper inside the colon's pathway.

While doctors are carefully considering the study conclusions, they continue to support colonoscopies as a vital weapon in the fight against colon cancer. This is a key point to remember during March, which is National Colorectal Cancer Awareness Month.

Importance of Colon Cancer Screening

ACS says colorectal cancer is the third most common cancer found in men and women in the US. Almost 108,070 new cases of colon cancer will be diagnosed this year; combined will rectal cancer, these conditions will attribute to approximately 50,000 deaths.

In recent years, the incidence rate of colon cancer has decreased by 2.3 percent annually, according to the US Centers for Disease Control and Prevention (CDC). The death rate also has continued to decrease, dropping 4.7 percent yearly.

Decreases in deaths and incidence rates have largely been attributed to the use of a colonoscopy as a screening tool. When colon cancer is diagnosed early and treatment begins immediately, patients enjoy a five-year relative survival rate of 90 percent.

More importantly, screening for colon cancer plays a vital role in the prevention of colon cancer; it provides doctors with an opportunity to locate and remove pre-cancerous polyps.

"We know the incident rate has been falling for close to a decade now, and that coincides with the increase in screening," Dr. Brooks says.

Canadian Research Study on the Use of Colonoscopy as a Screening  Tool

Results of the 2008 Canadian research study appeared to focus on the importance to ensure that doctors received thorough training in performing colonoscopies, says Dr. Bernard Levin, professor of gastrointestinal medicine and nutrition and vice president of cancer prevention at the University of Texas M.D. Anderson Cancer Center in Houston.

According to Dr. Levin, only 30 percent of the colonoscopies were performed  by gastroenterologists who were specifically trained to perform the procedure. The remaining colonoscopies were done by general surgeons or technicians who may or may not had received previous and adequate training in this field, he adds.

"It is not just a question of sticking a tube into the colon and looking around - it's not that simple. You have to have some training, and that training has to be specific," Dr. Levin says.

Dr. Brooks adds that the study has its drawbacks, because it looked at people who had received a colonoscopy at some earlier point, and died of colon cancer. "It may be there was no evidence of cancer at the time of the examination, and then cancer developed later," he says.

There is also no evidence on how well-prepared the patients were for their colonoscopy,  Dr. Levin says. If their colons were not thoroughly cleaned out ahead of time, cancers and polyps could have been missed. Drs. Levin and Brooks agreed that the Canadian study probably overstated the problem.

"Colonoscopy is not 100 percent accurate even in the best of hands, but it's probably better than the Canadian study gives it credit for," Dr. Levin says.

Is There a New Screening Tool for Colon Cancer?

While colonoscopy continues to remain the best method to detect colon cancer, recent studies have shown that other methods appear to be promising.

For instance, a research study found that virtual colonoscopy - in which the colon is examined through CT scans -  was effective in discovering 90 percent of precancerous lesions larger than 10 millimeters. According to Dr. Levin this procedure could be a good screening tool, especially for people with average risk of colon cancer.

"Five millimeters and below, it is likely virtual colonoscopy is not as accurate, but so what?" Dr. Levin says. "If you miss seeing one of those, it's likely its growth with not be significant, and it does not pose a significant cancer risk. You would pick it up the next time you undergo this procedure."

Always consult your physician for more information.

Colonoscopy and Colorectal Cancer

Colonoscopy is a diagnostic procedure that allows the physician to examine the entire length of the large intestine.

Colonoscopy can assist in identifying problems with the colon, such as early signs of cancer, inflamed tissue, ulcers, and bleeding. This procedure has been used to examine colon polyps, tumors, ulceration, inflammation, diverticula (pouches), strictures (narrowing), and foreign objects within the colon. It may also be used to determine the cause of unexplained chronic diarrhea or gastrointestinal bleeding or to evaluate the colon after cancer treatment.

During a colonoscopy, a long, flexible, lighted tube called an endoscope (also called a colonoscope), is inserted through the rectum into the colon. In addition to allowing visualization of the internal colon, the colonoscope enables the physician to irrigate, suction, inject air, and access the bowel with surgical instruments.

During the procedure, the physician may remove tissue for further examination and possibly treat any problems that are discovered.

A colonoscopy is also used to screen for colorectal cancer, the second leading cause of cancer deaths in the US.

Colorectal cancer is malignant cells found in the colon or rectum. The colon and the rectum are part of the large intestine, which is part of the digestive system. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum may also spread to other parts of the body.

The following complaints are the most common symptoms of colorectal cancer. However, each individual may experience symptoms differently:

• a change in bowel habits such as diarrhea, constipation, or narrowing of the stool that lasts for more than a few days
• rectal bleeding or blood in the stool
• cramping or gnawing stomach pain
• decreased appetite and vomiting
• weakness and fatigue
• jaundice - yellowing of the skin and eyes

People who have any of these symptoms should check with their physicians, especially if they are over 50 years old or have a personal or family history of the disease.

Symptoms of colorectal cancer may resemble other conditions, such as infections, hemorrhoids, and inflammatory bowel disease. It is also possible to have colon cancer and not have any symptoms. 

It is important to remember that colorectal cancer is the third most common cancer in both men and women. The number of deaths due to colorectal cancer has decreased, which is attributed to increased screening and polyp removal.

Other related procedures that may be used to assess problems of the colon include abdominal x-ray, computed tomography (CT scan) of the abdomen, abdominal ultrasound, barium enema, and sigmoidoscopy.

Always consult your physician for more information.