Why is screening for colorectal cancer important?
Colorectal cancer is the second most common cause of cancer related deaths in North America. Each year about 60,000 individuals are expected to die from the disorder and close to 150,000 new cases are diagnosed each year.
In the early stages, colon cancer presents with no symptoms. In the majority of cases, the early beginnings of a colorectal cancer are a small polyp. These small balloon-like tissues usually start of as very small flat lesions but over a 3-10 year period can progress to cancer. Not all polyps are cancerous and it is estimated that about 8-10% of untreated polyps will become malignant. The major risk factor in a polyp becoming a cancer is its size. Small polyps have no risk of cancer but when they are greater than 10-20 mm, the risk is increased significantly.
The purpose of the Virtual Colonoscopy is to screen the patient for the smaller polyps and have them removed them before they have the chance to grow large and become cancerous. Studies do indicate that removal of precancerous polyps reduces the incidence of colorectal cancer by at least 40%. For those who have a localized polyp which is malignant, the 5 year survival is excellent, but for those in whom the polyp has grown large and the patient is symptomatic, the 5 year survival is very low.
Who is at risk for colorectal cancer?
Colorectal cancer is quite common in North America and it is estimated that at least 1 in 20 individuals will develop the cancer in the course of a life time. The majority of these cancers occur in individuals over the age of 50.
Risk factors for colorectal cancer include:
Not modifiable factors
- History of colorectal cancer or adenomatous polyps.
- Family history of polyps. The risk of colorectal cancer is also significantly increased in individuals who have a first degree relative (child, parent, sibling) with the cancer).
- History of inflammatory bowel disease (Crohn's, ulcerative colitis).
- Certain genetically inherited disorders. There are also several familial syndromes which are known to increase polyps and associated with a high risk of cancer. However, most of these individuals are diagnosed much earlier in age and undergo routine surveillance.
Modifiable risk factors
There are several risk factors which may increase the risk of colon cancer and these include:
- obesity/weight gain
- physical inactivity
- poor nutrition
- excessive alcohol consumption
- diet high in fats and meats
- low fiber intake
What are the symptoms of colorectal cancer?
Generally, early colon cancer may have no symptoms but as the cancer grows some of the presenting features will be:
- altered bowel habits such as constipation
- blood in the stools or tissue paper
- abdominal cramps
- loss of appetite
- generalized fatigue
- Jaundice (yellow discoloration of skin and eyes)
- Loss of weight
Can colorectal cancer be prevented?
Unfortunately there is no cure for colorectal cancer but one can minimize the risk of getting the cancer with some preventive approaches. It is well known that changes in life style can significantly alter the risk of colon cancer and these include:
- avoid over eating and maintaining an ideal body weight
- eating a healthy diet of more fiber and less meat
- a diet low in saturated fats, meat and high in fiber content
- stop smoking
- avoid excessive alcohol intake
- Regular exercise
Who should have a colorectal screening?
The American Cancer Society recommends patients seek colorectal cancer screening as early as age 50 and every 3-5 years thereafter. Patients with a strong family history of colorectal cancer or polyps should be screened more often. High-risk patients should begin the above screening intervals starting at age 40.
What other tests are available for screening of colorectal cancer?
a. Fecal occult blood test plus a flexible sigmoidoscopy has been recommended every 5 years.
In this test, stool samples are collected in a small plastic container and analyzed in a laboratory for the presence of blood. The flexible sigmoidoscopy can only assess the lower rectum and colon for polyps. Both these tests can miss a lot of cancers and false positives can occur (conditions like hemorrhoids and rectal ulcers may also bleed). Data reveals that this test only prevent 12-16% of colorectal cancers.
b. Flexible Sigmoidoscopy every 5 years
The sigmoidoscopy can only evaluate the bottom 20-24 inches of colon and rectum. The scope is inserted in the rectum and generally does not require sedation. The technique is not very sensitive for screening colon cancers and data reveals that it may miss 15-20% of colon cancers.
c. Double-contrast barium enema every 5-10 years
Another technique which has been used to screen for polyps is a double contrast enema. In this study, barium is inserted into the rectum and the colon. X rays are than obtained. The technique is useful for large polyps (>10mm) but does have a tendency to miss smaller polyps (less than 8 mm). In addition, biopsy of the polyp is not possible with the technique.
d. Conventional colonoscopy every 10 years
This is an excellent technique for visualizing the entire colon with a colonoscope which is inserted into the rectum. The technique does require sedation and some abdominal discomfort from the injection of air into the colon. The technique does allow one to remove or biopsy the polyp with a snare. Small polyps can sometimes be missed with this technique and in rare circumstance, bowel perforation can occur. The technique is the gold standard for evaluation of polyps but is more invasive than all the other available techniques.
By ScanDirectory.com Staff
Updated: July 30, 2007