OAKLAND, Calif. A study of nearly 315,000 colonoscopies performed by 136 gastroenterologists found that adenoma detection rates closely tracked the future risk of colorectal cancer. The study was published April 3 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. This study also supports that finding and taking out adenomas prevents cancers, and finding more of them likely prevents more 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. It was undertaken within the National Cancer Institutes Population-based Research Optimizing Screening through Personalized Regimens (PROSPR) consortium, a multisite effort to evaluate and improve cancer-screening processes; Kaiser Permanente Northern California is a lead site for this study.

Colorectal cancer is the second leading cause of cancer deaths 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 between Jan. 1, 1998, and Dec. 31, 2010, in Kaiser Permanente Northern California, a large, integrated health-care delivery system. All patients were age 50 or older and had between 6 months and 10 years of follow up after their colonoscopy. The gastroenterologists were experienced: all had completed at least 300 colonoscopies, each performed an average of 2,150 colonoscopies per year, and almost all meet national guidelines for adenoma detection.

Among the nearly 315,000 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.

The adenoma detection rates varied from 7.4% to 52.5%, and for each 1% increase in adenoma detection rate there was a 3% decrease in colorectal cancer risk.

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.

Kaiser Permanente can conduct transformational health research such as this study in part because it has the largest private patient-centered electronic health system in the world. The organizations electronic health record system, Kaiser Permanente HealthConnect, securely connects 9.1 million patients to 16,000 physicians in almost 600 medical offices and 38 hospitals. It also connects Kaiser Permanentes research scientists to one of the most extensive collections of longitudinal medical data available, facilitating studies and important medical discoveries that shape the future of health and care delivery for patients and the medical community.

This research was supported by grants from the Kaiser Permanente Community Benefit Program and the National Cancer Institute.

In addition to Dr. Corley, co-authors of the study were Christopher D. Jensen, PhD, Amy R. Marks, MPH, Wei K. Zhao, MPH, Jeffrey K. Lee, MD, Jolanda de Boer, MB, Bruce H. Fireman, PhD, Theodore R. Levin, MD, and Charles P. Quasenberry, PhD, all of Kaiser Permanente Division of Research; Joanne E. Schottinger, MD, Virginia P. Quinn, PhD, and Nirupa R. Ghai, PhD, all of Kaiser Permanente Southern California Research and Evaluation; Chyke A. Doubeni, MD, MPH, University of Pennsylvania Perelman School of Medicine; and Ann G. Zauber, Memorial Sloan-Kettering Cancer Center.