Effective and safe – Evaluation of the first ten years of colonoscopy in cancer screening

In 2002, Germany was one of the first countries worldwide to introduce colonoscopy as part of its national statutory cancer screening program. Scientists from the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) have now looked back on the first ten years of this program to evaluate its effectiveness: how many cases of cancer did it prevent? How many tumors were detected early in the course of the disease? And what about cases of over-diagnosis, where the method indicated a malignancy that would not have become clinically significant during a person’s lifetime?

In the current study, the researchers evaluated the medical reports of 4.4 million screening colonoscopies conducted between 2003 and 2012. “This is the most comprehensive evaluation of a[s1]  national screening colonoscopy program to date,” says study head Prof. Hermann Brenner of the DKFZ, who was in charge of the study.

The calculations are based on a mathematical model that takes into account not only medical reports and mortality rates, but also other factors such as the incidence of different types of precancerous lesions and the course of time over which they turn into colorectal cancer.

During these first ten years of endoscopic gastrointestinal screening, a total of 180,000 precancerous lesions were discovered and immediately removed during the examination. Additionally, physicians found over 40,000 cases of early-stage colorectal cancer, a phase in which the disease is still curable in most cases. In contrast, there were only about 4,500 cases of over-diagnosis.

“In about one out of 28 colonoscopy examinations, a physician finds a precancerous lesion and thus prevents a cancer case,” says Dr. Michael Hoffmeister, one of the authors of the publication. “In one out of 121 examinations, doctors detect a malignant tumor early on. But only one out of 1,089 examinations leads to an over-diagnosis.” He adds: “In participants under 75 years of age, only 0.4 percent of gastrointestinal endoscopic exams result in an over-diagnosis. This means that colonoscopy screening produces significantly better results than other cancer screening programs. Mammography, for example, has a much higher over-diagnosis rate.”

Endoscopic examinations have the highest chance of preventing a case of cancer if conducted at around the age of 60 years. Increasing age of the subjects is accompanied by a rise in the rate of over-diagnosis.

Brenner’s conclusion is crystal clear: “In the long term, colonoscopy will lower colorectal cancer mortality. Moreover, endoscopic screening is a real means of prevention. As opposed to other screening programs, it will also significantly lower the incidence of new cancer cases.”

Hermann Brenner, Lutz Altenhofen, Christian Stock, Michael Hoffmeister: Prevention, Early Detection, and Overdiagnosis of Colorectal Cancer Within 10 Years of Screening Colonoscopy in Germany. Clinical Gastroenterology and Hepatology 2014, DOI: 10.1016/j.cgh.2014.08.036