A single sigmoidoscopy between ages 55 and 64 can reduce deaths from colorectal cancer by at least 43 percent, British researchers reported Tuesday.
The results from the first large randomized trial of sigmoidoscopy show that it is a more effective tool than mammography for breast cancer or PSA tests for prostate cancer, and confirm current U.S. guidelines suggesting regular sigmoidoscopy or colonoscopy to screen for colorectal cancer.
“If sigmoidoscopy can yield these results, colonoscopy should yield even better results” because it explores the entire bowel, said Dr. Eric Esrailian, a gastroenterologist at UCLA’s Reagan Medical Center.
“We don’t often use the word ‘breakthrough,’ but this is one of those rare occasions when I am going to use that word,” Harpal Kumar, chief executive of Cancer Research UK, said in a news conference. “It is extremely rare to see the results of a clinical trial which are quite as compelling as this one.”
The test not only identifies tumors in their early stage of development, when cure rates are about 90 percent, but also identifies and allows removal of polyps that may later grow into tumors. Currently, only about 13 percent of all tumors are detected at that stage. And when symptoms develop, the cure rate is less than 50 percent.
“There has never been clinical trial evidence that removing polyps prevents cancer,” said Dr. Wendy Atkin of Imperial College London, lead author of the new study, which was reported online in the journal Lancet. “There’s been lots of indirect evidence, but this will be the first direct evidence.”
Beginning in 1994, Atkin and her colleagues enrolled about 170,000 men and women at 14 centers in Britain. About two-thirds were assigned to the control group and the rest to undergo sigmoidoscopy. An estimated 71 percent of those assigned to the intervention actually underwent the procedure, in which a flexible tube with a small camera is inserted through the rectum to examine the lower third of the bowel, where more than half of all bowel cancers occur.
Polyps – fleshy protuberances that are often precursors of tumors – were snipped out with a special tool inserted through the tube.
After 11 years of follow-up, the incidence of colorectal cancer in those who actually underwent the procedure was reduced by 31 percent and deaths by 43 percent.
At least three other large studies of screening by sigmoidoscopy are in progress in the United States, Norway and Italy.
“The question remains whether performing the test more frequently might lead to more impressive decreases in mortality,” said Dr. Durado Brooks, director of prostate and colorectal cancer for the American Cancer Society.
U.S. recommendations call for a colonoscopy – in which the entire length of the large intestine is examined – every 10 years after the age of 50 if it reveals no abnormalities or a sigmoidoscopy every five years.
Sigmoidoscopy has fallen into some disfavor, however, because reimbursement often does not cover a physician’s costs, Brooks said. There is also a perception that colonoscopy is better, “which is not necessarily supported by the evidence,” he added.