Flexible Sigmoidoscopy Decreases Incidence of Colorectal Cancer
Colorectal cancer, or bowel cancer, is the second main cause of cancer-related deaths in the United States. It generally occurs due to the uncontrolled growth of cells in rectum, appendix or colon. Common symptoms are bleeding, anemia, weight loss and change in bowel habits.
Flexible sigmoidoscopy is used to diagnose colorectal cancer. It is also used for the detection of the underlying cause of symptoms like abdominal pain and discomfort, bleeding from rectum, etc.
The procedure is done using a sigmoidoscope. A sigmoidoscope is a thin, long flexible tube about ½ inch in diameter used to view the inner lining of rectum and lower 1/3rd of colon-called the sigmoid colon. Sigmoidoscopy used as a screening test reduces the rates of new cases and deaths due to colorectal cancer. Flexible sigmoidoscopy and colonoscopy are more effective than fecal occult blood testing in diagnosing polyps that may result in colorectal cancer.
The risk of colorectal cancer is reduced by the removal of pre-cancerous polyps by sigmoidoscopy.
Robert Schoen and colleagues conducted a study spanning over 20 years, where they discovered that mortality of colorectal cancer was lowered by about 26 percent and rate of new cases was decreased by 21 percent owing to sigmoidoscopy screening.
The study was published in the New England Journal of Medicine, 2012.
One of the experts said, "The most important message is that, regardless of modality chosen, colorectal cancer screening lowers mortality from colorectal cancer, and all individuals 50 and over should be screened."
The large randomized population-based study was designed to assess the effects of screening on colorectal cancer-related mortality.
About 154,900 males and females aged between 55-74 years were enrolled for the study between the years 1993 and 2001.
The participants were divided into two groups. One group was offered screening with flexible sigmoidoscopy -once at the beginning of the study and then after three to five years. The second group was subjected to usual care.
The participants were traced for about twelve years for collecting data of cancer diagnosis and deaths.
The colorectal cancer incidence and mortality in the two groups was compared.
Over a span of twelve years, in the screening group, a decrease of 21 percent in colorectal incidence was noticed while a decline of 26 percent was recorded in colorectal cancer mortality. Detected cancers were mostly in the early stages; about 75 percent were in stage I or II.
In the group that underwent screening, a 50 percent reduction in mortality due to distal colorectal cancer was reported. No significant reduction in deaths occurred due to proximal colorectal cancer. However, there was a decline of 14 percent in the incidence of proximal colorectal cancer.
Barnett Kramer, M.D. and director of NCI's Division of Cancer Prevention, mentioned, "This is the second major trial that has shown that sigmoidoscopy is effective in reducing the risk of dying of colorectal cancer. Sigmoidoscopy is less invasive than colonoscopy and carries a lower risk of the colon being perforated, which may make it more acceptable as a screening test to some patients. There are several effective screening tests for colorectal cancer, and the most effective screening test is the one that people choose to take."
The study thus concluded that flexible sigmoidoscopy is associated with a reduction in colorectal cancer incidence and mortality, especially related to cancers of the distal colon.
Colorectal-Cancer Incidence and Mortality with Screening Flexible Sigmoidoscopy; Robert Schoen et al; NEJM 2012