Fecal Occult Blood Screening Increases High-Risk Polyp Detection

The introduction of biennial colorectal cancer screening in a region of France increased the rate of diagnosis of high risk precancerous adenomas, sometimes called polyps, by 89%.

As part of the screening program, a prescreening procedure is undertaken by a general practitioner or gastroenterologist to identify patients who are at higher than average risk of colorectal cancer based on their family history and those patients were invited to undergo colonoscopy rather than fecal occult blood test (FOBT).

Scientists at the University of Burgundy (INSERM Unité 866; Dijon, France) evaluate the rate of diagnosis of adenomas before and after the initiation of a screening program using fecal occult blood testing that began in 2003. The study included all residents aged between 50 and 74 years of age who had a first adenoma identified between January 1997 and December 2008. The investigators showed that 38.7% of these people had high-risk adenomas, meaning they were larger than one centimeter in diameter, involved the finger-like projections called villi in the intestinal lining, or exhibited a high grade of dysplasia.

Of 1,179 patients studied, 889 underwent colonoscopy, and overall, 253 colorectal neoplasias were diagnosed including 35 cancers, and adenomas in 219 patients. A total of 209 advanced adenomas were diagnosed. The authors calculated that the positive predictive value of colonoscopy was 3.9% for cancer, 12.9% for advanced adenoma, and 25% for adenoma overall. This compared poorly to the positive predictive value in the average risk population selected by a positive FOBT. In this population, the positive predictive value of the colonoscopy done after positive test in their administrative area ranges from 7.5% to 10% for cancer, from 15% to 27% for advanced adenoma and between 32% and 37% for adenoma. The immunochemical fecal occult blood tests outperformed guaiac tests for the detection of colorectal cancer and advanced adenoma. They have doubled the detection rate of invasive colorectal cancer, mostly at early stages, and led to a fourfold increase in the detection rate of noninvasive colorectal cancer and advanced adenomas.

Hans-Joachim Schmoll, MD, PhD, a professor of Hematology and Oncology, at the Martin Luther University Halle-Wittenberg (Halle, Germany) said, “In this study it was shown that a prediction for screening colonoscopy using high risk features—based on family history—revealed a less positive predictive value than prescreening by FOBT with follow-up of those who have a positive result.” The study was presented at the European Society for Medical Oncology Congress held September 26–30, 2014, in Madrid (Spain).

Related Links:
University of Burgundy 
Martin Luther University Halle-Wittenberg