Single Sigmoidoscopy Can Prevent Cancer, Save Lives
For the first time, scientists have direct clinical evidence that removing polyps from the colon can prevent cancer and save lives. The procedure that makes this possible is a single sigmoidoscopy, performed between ages 55 and 64, according to British researchers in a study released online in advance of publication in an upcoming print issue of The Lancet.
A sigmoidoscopy is a procedure in which doctors can explore the large intestine using a flexible tube that is connected to a fiberoptic camera. A light transmitted through the scope allows clinicians to view the intestine through an eyepiece or video screen. The procedure is the best way to diagnose colon cancer, although it is also used to investigate bleeding and abdominal pain.
In the United States, experts recommend that adults older than 50 undergo a sigmoidoscopy every five years. The more invasive colonoscopy, in which clinicians use the tube to explore the entire length of the large intestine, is an option and is recommended every 10 years.
British researchers, however, report that just one sigmoidoscopy can reduce deaths from colorectal cancer by at least 43 percent. A sigmoidoscopy can identify early-stage tumors, when cure rates are about 90 percent, and also allows physicians to remove polyps (fleshy growths) that may later develop into tumors.
The American Cancer Society (ACS) estimated that 106,100 new cases of colon cancer and 40,870 new cases of rectal cancer would be diagnosed in 2009. Colorectal cancer is the third leading cause of cancer-related deaths in the United States, and expected deaths in 2009 were 49,920. Lifetime risk for developing colorectal cancer is about 1 in 19. The ACS reports that only about 50 percent of adults who should be checked for colorectal cancer actually undergo screening.
Dr. Wendy Atkin of Imperial College London, the study’s lead author, and her team enrolled about 170,000 men and women at 14 centers throughout Britain in 1994. Approximately two-thirds were in a control group and the remaining individuals underwent sigmoidoscopy. About 71 percent of those assigned to receive the procedure actually had it done.
Eleven years later, the researchers discovered that the incidence of colorectal cancer among those who had the procedure was reduced by 31 percent and deaths by 43 percent. Because most people have developed all the polyps they will ever have by the time they are in their mid-50s, Atkin said “there is no sign that the effect of the test is wearing off,” and that for a test that lasts only a few minutes, “the benefit may last a lifetime.”
Sigmoidoscopy and colonoscopy are screening procedures many people avoid because they fear pain and discomfort. A sigmoidoscopy is more convenient and less unpleasant than a colonoscopy because there is no need for sedation, patients need to take only an enema on the morning of the test rather than intestinal-cleansing products, and the procedure can be done in the office.
The results of the UK study indicate that a single sigmoidoscopy can result in a significant reduction in colorectal cancer and save lives. At least three other large studies utilizing sigmoidoscopy screening are currently underway in the United States, Italy, and Norway. The US study involves repeat sigmoidoscopies every three years, and the results are not expected for a year or two.
American Cancer Society
The Lancet online, April 27, 2010