Natural Medicine Clinic Publications

Colorectal Cancer Screening: What is it? When should you do it?

By Nancy Aagenes, ND

The importance of screening:

• Colorectal cancer is more common in women that uterine, ovarian and cervical cancer.
• Colorectal cancer is the third-leading cause of cancer death among US women.
• Only 37% of colorectal cancers are detected early.

The difficulty of screening:

• By definition a "screening test" has a high degree of sensitivity (it measures well what we want measured), high degree of specificity (it measures only what we want measured) and it is inexpensive enough that we can do it in a large population.
• There is no test for colorectal cancer that meets these criteria.

How the cancer develops:

• Slowly. Adenomatous polyps-grape like growths-form on the inner lining of the colon and rectum. Eventually they destroy and invade surrounding tissue. However, from initial appearance of the polyp to cancer is a progression that takes approximately 10 years.

Risk factors:

• Average risk -50 years or older, no symptoms and no other risk factors.
• Increased risk -immediate family members (Mom, Dad, brothers, sisters) diagnosed with colorectal cancer or an adenomatous polyp, family history of adenomatous polyposis, family history of hereditary non-polyposis colorectal cancer, or personal history of inflammatory bowel disease.
• Other risk factors include lack of exercise, obesity, high fat low fiber diet, tabacco use and excessive alcohol consumption.

Signs and symptoms of colorectal cancer-rectal bleeding, blood in the stools, unexplained change in bowel habits. Other things can also cause these symptoms and must be ruled out.

Screening tools:

• Fecal occult (hidden) blood testing every year. Only 5 to 10% of those with a positive test will actually have cancer. Remember that if you test indicates a possible problem, additional screening becomes urgent, even tho less than one in ten will have cancer. There are many reasons that blood can be in the stool that do not involve cancer.
  
  This test is also poor at assuring us nothing is wrong. You can test okay and still have cancer.
  
  Why is it used if it is such a poor test? When it is positive insurance companies are more likely to pay for the colonoscopy, which is the most expensive test. For those who can't afford the other tests it is at least something and it is affordable.
  
  Could its predictive value be higher if it were done annually?

• Colonoscopy every 10 years. This test can visualize the entire colon, detecting and removing polyps and doing biopsy for cancer. It has not been assessed for decreasing mortality, but is considered the most comprehensive test. Those who do the test, gastroenterologists, consider it the most reliable.

• Flexible sigmoidoscopy every five years-does not reach the upper one-third of the colon and can miss cancers there.

• Barium enema x-ray is used, but generally not recommended for this purpose.

What is currently recommended by the conventional standard of care in patients 50 and over?

• An occult blood annually every year 50 and older, and

• Either a sigmoidoscopy every five years

OR a colonoscopy every ten years.

What do the tests cost?

• Fecal occult blood test-less than $20 self pay.
• Sigmoidoscopy-about $150 or more self pay.
• Colonoscopy-about $800-1500 self pay.

The assumption that any screen individually or in combination decreases the number of deaths from colon cancer is strongly held. However, none of these tests or combinations has been scientifically assessed for decreasing mortality. This begs the questions: How many who wait until they have signs and symptoms have invasive cancer? Could someone pay attention to early symptoms and have the same mortality as those who screen?