Paris: A single exam of the rectum and lower colon between the age of 55 and 64 slashes colon cancer mortality by more than 40 percent, according to research published Wednesday.
The 16-year study of more than 170,000 people in Britain also found that the one-time procedure cut incidence of the disease by a third compared to a control group that did not undergo the examination.
The relatively simple test "could massively reduce colorectal cancer incidence and mortality," the British medical journal The Lancet, which published the study, said in a press release.
The most effective and cost-efficient way to screen for various cancers -- including of the breast, prostate and colon -- has been hotly debated in recent years.
Colon cancer is the third most commonly diagnosed form of the disease worldwide, accounting for more than one million cases and 600,000 deaths annually.
The large majority of colon cancers arise from adenomas, a type of pre-malignant polyp that occurs in 20 to 30 percent of the population. Most people who develop the disease will have adenomas by the age of 60.
The new study provides the strongest evidence to date that a procedure known as a sigmoidoscopy, when performed in late-middle age, provides significant protection against the deadly cancer.
Generally performed without anaesthesia, flexible signoidoscopy allows a physician to examine the rectum and lower colon, called the signoid. Two-thirds of colorectal cancers develop in this region.
Growths, whether benign or cancerous, can be removed during the procedure.
The examination is less invasive -- and less costly -- than a full colonoscopy, in which the entire large intestine is looked at while the patient is under anaesthesia.
Many health systems currently screen for colon cancer by testing stool samples for the presence of blood, a procedure which has been shown to reduce mortality by 15 percent.
In the study, 170,432 men and women recruited between 1994 and 1999 were divided into two groups. Nearly 113,200 were assigned to the control group, and 57,237 to the intervention group.
During the screening period and an 11-year follow up, 2,524 participants were diagnosed with colon cancer, 1,816 in the control group and 706 in the intervention group. Incidence of the disease in people who were screened was cut by 33 percent, and mortality by 43 percent.
When results were confined to the rectum and lower colon, incidence was reduced by half. "Flexible sigmoidoscopy is a safe and practical test and, when offered only once to people between ages 55 and 64, confers a substantial and long-lasting protection from colon cancer," the authors concluded.
The exam, while far more expensive that checking for blood in the stool, may also be cost effective "largely because of the avoided costs of treatment resulting from the reduction in incidence", they added.
The researchers, led by Wendy Atkin of Imperial College London, speculate that the decrease in cancer rates and deaths in the test group will become even greater over time.
"If incidence in the screened participants remains low during further follow up, the magnitude of the reduction will continue to increase," they said.