In CRC Screening, Location Matters

Colonoscopy screening reduces mortality from cancers of the distal, but not proximal, colon, according to a study published in the October issue of Gastroenterology.

Harminder Singh et al. studied mortality from CRC among more than 55,000 people that had received screening colonoscopies, compared with the general population. They found that people who had received a colonoscopy exam were 29% less likely to die from colorectal cancer (CRC) 5–10 years later; they had a 47% reduction in death from cancer of the distal colon (even after more than 10 years), but no reduction in death from cancer of the proximal colon.

Colonscopy therefore significantly reduces risk of death from CRC, but the effect is not uniform for tumors that arise in different areas of the colon.

There are several reasons that colonoscopy screening doesn’t reduce mortality from certain tumor types. Tumors of the proximal colon have a higher miss rate than those of the distal colon—the proximal colon is harder to clean and prepare for an efficient examination. Proximal colon tumors are often flat lesions, which are harder for colonoscopists to detect, and have a worse prognosis—when they are detected, they are harder to treat.

This is the first study of differences in CRC mortality, based on colon region, among people screened by colonoscopy. The authors propose that in screening, practitioners more carefully examine the proximal colon, to increase early detection of tumors in this location and reduce mortality.

More Information on Colorectal Cancer Screening:

Read the article online:
Singh H, Nugent A, Demers AA, et al. The reduction in colorectal cancer mortality after colonoscopy varies by site of cancer. Gastroenterology 2010;139:1128–1137.

Read the complementary Clinical Gastroenterology and Hepatology article:
Hassan C, Pickhardt PJ, Rex DK. A resect and discard strategy would improve cost-effectiveness of colorectal cancer screening. Clin Gastroenterol and Hepatol 2010;8:865–869.

About Kristine Novak, PhD, Science Editor

Dr. Kristine Novak is the science editor for Gastroenterology and Clinical Gastroenterology and Hepatology, both published by the American Gastroenterological Association. She has worked as an editor at biomedical research journals and as a science writer for more than 12 years, covering advances in gastroenterology, hepatology, cancer, immunology, biotechnology, molecular genetics, and clinical trials. She has a PhD in cell biology and an interest in all areas of medical research.
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