A study of over 224,000 patients and more than 314,000 colonoscopies found that adenoma detection rates closely tracked the future risk of colorectal cancer. The study was published in The New England Journal of Medicine.
Colonoscopies screen for colorectal cancer by detecting early, curable cancers. Precancerous adenomas—a type of colon polyp—can also be detected and removed, thereby preventing cancers from developing.
"We found that higher levels of detection were associated with a decreased subsequent risk of cancer," said Douglas A. Corley, MD, PhD, a gastroenterologist and research scientist with the Kaiser Permanente Division of Research. "Taking out adenomas prevents cancers, and early detection likely prevents many cancers."
The study is the largest ever conducted and the first in the United States to examine the relationship between detecting adenomas and the future risk of colorectal cancers.
Colorectal cancer is the second-leading cause of cancer death in the United States. According to the American Cancer Society, about 137,000 new cases are diagnosed each year in the United States with 50,000 deaths. Colonoscopy every 10 years is one of three screening methods recommended by the U.S. Preventative Services Task Force; the others are sigmoidoscopy every 5 years or annual fecal testing.
The colonoscopies studied were performed on Kaiser Permanente patients between Jan. 1, 1998, and Dec. 31, 2010, in Northern California. All patients were age 50 or older and had at least 6 months of follow-up after their colonoscopy. The gastroenterologists were experienced: All had completed at least 300 colonoscopies, and each performed an average of 2,150 colonoscopies per year.
Among the nearly 264,972 colonoscopies studied, 712 patients were subsequently diagnosed with a colorectal cancer after being followed for up to 10 years after their exam; these included 255 advanced-stage cancers and 147 deaths.
Researchers found that for each 1 percent increase in adenoma detection rate, there was a 3 percent decrease in colorectal cancer risk.
Dr. Corley said the study confirms that adenoma detection rates are an accurate quality metric for clinicians performing colonoscopies: "Given these results, to maximize the effectiveness of our screening programs, we have been providing feedback to physicians for three years as well as developing new methods to maximize detection rates."