ASK THE DOCTOR: Getting screened for colon cancer
By DR. JIM MITTERANDO
The Patriot LedgerQ. Now that I am 50 years old I understand that I need to be screened for colon cancer. Which test should I have - a colonoscopy or sigmoidoscopy? What is a barium enema?
A. At age 50, you have a 5 percent (1 in 20) chance of developing cancer during your lifetime and a 2.5 percent (1 in 40) chance of dying of colon cancer. Screening for colon cancer can detect precancerous colon polyps or find an early cancer before it has spread.
Which technique is preferred for screening for colon cancer (rectal exam, barium enema, flexible sigmoiscopy and colonoscopy) has been an ongoing dialogue in the medical community. The key is to have some sort of screening and discuss with your health care provider which one may be right for you.
The American Cancer Society recommends yearly rectal examinations beginning at age 50. During the rectal exam, stool is tested for microscopic traces of blood that can be a sign of cancer or polyps.
Both sigmoidoscopy and colonoscopy use a flexible tube that is inserted in the rectum to examine the large intestine for cancers or precancerous polyps. During the examination, air is inserted to expand the colon. Some cramping and discomfort occurs. If a polyp is seen, a biopsy is taken and sent to the pathologist for examination.
Sigmoidoscopy is done in the doctor's office and screens the lower 1/3 to 1/2 of the colon. It requires no sedation and some mild preparation with enemas or suppositories to clear out the colon. The procedure lasts about 15 minutes. Five minutes after the examination, you no longer feel any gas and people go to work or continue their day without any complaints. Eight percent of people will have a polyp discovered during a sigmoidoscopy that will then require a follow up colonsocopy.
Colonoscopy examines the entire colon but requires more extensive preparation to clean out the bowel including a clear liquid diet the day before the procedure. The procedure lasts about 30 minutes. Colonsocopy requires intravenous sedation at an outpatient center and takes most of the day to recover from the anesthesia, requiring a day off from work. The risk of perforating the colon is 1 in 1,000 during colonoscopy compared to a 1 in 10,000 risk during sigmoidoscopy.
Barium enema involves a radiologist inserting dye into the rectum and taking X-ray pictures that examine the entire colon. This procedure requires preparation to clean out the colon, similar to the colonoscopy, and lasts about 30 minutes involving some cramping. It takes several days to pass the barium. Barium enemas are not used as frequently since they may not detect smaller polyps and cancers and biopsies cannot be obtained during the procedure.
The American Cancer Society recommends flexible sigmoidoscopy or barium enema every five years at age 50 or colonoscopy every 10 years to screen for colon cancer in asymptomatic persons without family history. It also recommends colonoscopy screening in people with higher risk such as a strong family history beginning at age 40 with screening intervals to be determined by the person's individual risks.
The debate concerns which test is best in screening for colon cancer. Some focus on the fact that a sigmoidoscopy does not examine the entire colon compared to a colonoscopy or barium enema.
Most people who have precancerous polyps will have a polyp in the lower colon detected by flexible sigmoidoscopy which alerts the physician to examine the upper colon with a colonoscopy. Recent studies indicate that isolated upper colon polyps could go undetected with sigmoidoscopy in only 1 percent of people who have a normal lower colon exam by sigmoidoscopy.
There are no studies to determine that a colonoscopy and extra detection will ultimately lower cancer death and until that is resolved, it is up to individuals and their physicians to make the decision.
I often recommend sigmoidoscopy as the preferred screening test that avoids the increased inconvenience and risk of colonoscopy. I do not want to subject people to more aggressive evaluations and treatments unless evidence shows a long-term benefit.
Many people ask me about alternatives they have read about including virtual colonoscopy that involves CT scans or swallowable mini-cameras. These are experimental tests currently not available.
Dr. Jim Mitterando is a family doctor at Health Care South/Cohasset Family Practice and a staff member at South Shore Hospital in Weymouth.
Readers should send questions to: Ask the Doctor, The Patriot Ledger, P.O. Box 699159, Quincy, MA 02269-9159, or by E-mail to his attention at features@ledger.com. The information in this column is not intended to diagnose individual conditions. Readers should see their own doctors about specific problems.
Editor's note: This is the first column by Dr. Mitterando, who is taking over "Ask the Doctor."
Copyright 2000 The Patriot Ledger