Sigmoidoscopy an option for colon cancer screening
This analysis, led by Dr. Robert Schoen from the University of Pittsburgh Medical Center, involved 154,900 adults age 55 to 74 who were offered either two sigmoidoscopies, three or five years apart, or no colon cancer screening.
Over the next 12 years, there were 1,012 new cases of colon cancer in the screening group and 1,287 in the unscreened group. In addition, there were 252 related deaths among people offered sigmoidoscopy, compared to 341 in the unscreened group.
The lower mortality in the screening group seemed to be attributable entirely to fewer deaths from so-called distal colon cancer, which occurs in the part of the intestines closer to the rectum. There was no difference between the two groups in deaths from proximal colon cancer, which is cancer higher up in the intestines and beyond the reach of the sigmoidoscopy scope.
How many people are being screened for colorectal cancer?
Unfortunately, screening rates are too low. In a recent survey of Americans over 50 conducted by the Centers for Disease Control, only 41percent reported having had either an FOBT (the take-home stool card test) or a partial colon exam (by sigmoidoscopy) within the time intervals recommended by major professional groups such as ASGE. Given the preventable nature of this cancer, we can and must do better! For comparison, 86 percent of women are screened for breast cancer. The American Cancer Society has a goal for 75 percent of adults aged 50 and over to get screened by 2015.
Some reasons for low colorectal cancer screening rates include:
- Lack of public awareness about colorectal cancer and the benefits of regular screening
- Inconsistent promotion of screening by medical care providers
- Uncertainty among healthcare providers and consumers about insurance benefits
- Characteristics of the screening procedures (e.g., imperfect tests, negative attitudes towards the screening procedures)
- Hesitance to discuss “the disease down there”
FALSE POSITIVES COMMON
The screening tests were not without their limitations. One in five men and one in eight women had a false-positive sigmoidoscopy, which resulted in more invasive testing that ultimately found no pre-cancers or cancers. In addition, 22 people suffered a bowel perforation either from the initial sigmoidoscopy or a follow-up colonoscopy.
A limitation of the trial itself is that the two study groups weren’t as different as the researchers initially intended: almost half of people in the group assigned to no screening ended up getting a sigmoidoscopy or colonoscopy on their own during the study.
Trials in the UK and Italy have also suggested screening with sigmoidoscopy can reduce deaths from colon cancer.
Because of that, the UK plans to offer sigmoidoscopies free of charge to all adults in their mid-50s within the next five years, according to Wendy Atkin, a professor of gastrointestinal epidemiology at Imperial College London, who worked on the UK study.
“We need to revisit sigmoidoscopy in the United States,” Atkin told Reuters Health.
Flexible sigmoidoscopy
During this test, the doctor looks at part of the colon and rectum with a sigmoidoscope - a flexible, lighted tube about the thickness of a finger with a small video camera on the end. It is inserted through the rectum and into the lower part of the colon. Images from the scope are viewed on a display monitor.
Using the sigmoidoscope, your doctor can view the inside of the rectum and part of the colon to detect (and possibly remove) any abnormality. Because the sigmoidoscope is only 60 centimeters (about 2 feet) long, the doctor is able to see the entire rectum but less than half of the colon with this procedure.
Before the test: You will need to have a bowel preparation to clean out your lower colon. The colon and rectum must be empty and clean so your doctor can view the lining of the sigmoid colon and rectum. Your doctor will give you specific instructions to follow. You may be asked to follow a special diet (such as drinking only clear liquids) for a day before the exam. You may also be asked to use enemas or to use strong laxatives to clean out your colon before the exam. Be sure your doctor is aware of any medicines you are taking, as you may need to change how you take them before the test.
During the test: A sigmoidoscopy usually takes 10 to 20 minutes. Most people do not need to be sedated for this test, but this may be an option you can discuss with your doctor. Sedation may make the test less uncomfortable, but it requires some time to recover from it, as well as having someone with you to take you home after the test.
You will likely be asked to lie on a table on your left side with your knees positioned near your chest. Your doctor should do a digital rectal exam, or DRE (inserting a gloved, lubricated finger into the rectum), before inserting the sigmoidoscope. The sigmoidoscope is lubricated to make it easier to insert into the rectum. The scope may feel cold. The sigmoidoscope may stretch the wall of the colon, which may cause bowel spasms or lower abdominal pain. Air will be placed into the sigmoid colon through the sigmoidoscope so the doctor can see the walls of the colon better. During the procedure, you might feel pressure and slight cramping in your lower abdomen. To ease discomfort and the urge to have a bowel movement, it helps to breathe deeply and slowly through your mouth. You will feel better after the test once the air leaves your colon.
If a small polyp is found during the test your doctor may remove it with a small instrument passed through the scope. The polyp will be sent to a lab to be looked at by a pathologist. If a pre-cancerous polyp (an adenoma) or colorectal cancer is found during the test, you will need to have a colonoscopy at a later date to look for polyps or cancer in the rest of the colon.
Possible complications and side effects: This test may be uncomfortable because of the air put into the colon, but it should not be painful. Be sure to let your doctor know if you feel pain during the procedure. You might see a small amount of blood in your first bowel movement after the test. Significant bleeding and puncture of the colon are possible complications, but they are very uncommon.
Research suggests nurses can do the less-invasive test, she said. It’s also significantly cheaper than colonoscopy - at roughly $150, compared to about $1,000 for a colonoscopy.
Schoen doesn’t expect colonoscopy to go out of style as the most popular method for colon cancer screening in the U.S. But, he added, flexible sigmoidoscopy as an initial test is a good choice for some people who want to avoid a colonoscopy unless it’s completely necessary.
“Absolutely it’s an option on the table,” he told Reuters Health.
“If someone, for example, was afraid of anesthesia, if they want a test where the prep is not so aggressive - they just take enemas as opposed to drinking laxatives, if they cannot spare a day… all those are good reasons if you want to go and have a (sigmoidoscopy),” Schoen said.
Neugut told Reuters Health many U.S. doctors don’t do the less-invasive procedures anymore. But data are lacking to prove colonoscopy is any better than initially going for sigmoidoscopy, he said.
“Anyone who doesn’t want to have a colonoscopy, they should consider sigmoidoscopy as certainly… a valid form of screening for colon cancer,” Neugut said.
SOURCE: New England Journal of Medicine, online May 21, 2012