Colorectal cancer screening: Nine different tests – but they deliver comparable results
The earlier colorectal cancer and its precancerous lesions are detected, the better. For this purpose, new immunological tests for hidden traces of blood in the stool have been in use since this year. These tests only deliver positive results if specific threshold values of hemoglobin are exceeded. Scientists from the German Cancer Research Center (DKFZ) in Heidelberg have compared nine of these tests. Their result: All nine tests detect the vast majority of colorectal cancer cases and also many of its precancerous lesions. However, the manufacturers' specifications of the hemoglobin value above which there is a suspected case of colorectal cancer vary widely. Adjusting the thresholds, the scientists showed that all tests deliver very similar results. Even a smartphone test that functions without laboratory analysis can compete with test results from the laboratory.
Colon cancer under the microscope
© Lutz Langbein, DKFZ
Colorectal cancer screening has become simpler and more reliable this year. Immunological tests detect hemoglobin – the protein that gives blood its red color – in the stool. This provides a clue pointing to a possible case of colorectal cancer or precancerous lesions in a patient. The fact that the immunological tests have replaced the less specific hemoccult test is essentially a result of research conducted by Hermann Brenner from the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ).
Presently, there are numerous different immunological tests on the market. "Until now, it has been unclear whether and how much the available tests differ from each other," said Brenner. Therefore, the epidemiologist and his team made a direct comparison of nine tests.
Brenner's result is that all nine tests detect the vast majority of colorectal cancer cases and also many precancerous lesions. If one sticks to the threshold values specified by the manufacturers for a test to be considered positive, then the rates of positive results vary widely.
However, when the scientists adjusted the threshold values in their evaluation, the tests all delivered very similar results. "In this work, we present, for the first time, a worldwide unique direct comparison of the diagnostic performance of a large number of quantitative tests in the same large group of study participants," Brenner said. He continued that these figures could be used to derive countrywide recommendations for threshold values for individual tests.
"In this work, Brenner and colleagues are giving precise recommendations for further improvements in colorectal cancer screening," emphasized Michael Baumann, DKFZ's Chairman and Scientific Director. "Since colonoscopy, which continues to be the gold standard in screening for colorectal cancer, is rather laborious, it is important to also offer people a screening examination with a lower threshold."
Five of the nine tests require analysis in a laboratory. The remaining four can be conducted and evaluated directly at the family doctor's or urologist's office. Even the test that uses a smartphone app for evaluation delivered reliable results, at least if it was carried out by qualified staff.
Colorectal cancer is the third most frequent type of cancer worldwide. Each year, approximately 1.4 million people are newly diagnosed with it; 700,000 succumb to the disease. It also holds true for colorectal cancer that the earlier it is detected, the better the chances are of curing it. Therefore, people insured with statutory health insurance in Germany are entitled to an endoscopic examination of the colon (colonoscopy) starting at 55 years of age. Colonoscopy is considered to be the most accurate method for detecting colorectal cancer and its precursors. However, the testing method is laborious and many patients are reluctant to have it done. Only 20 to 30 percent of those eligible actually take advantage of the screening examination.
New immunological testing methods that have been covered by statutory health insurance since April of this year are intended to help encourage more people to undergo a screening exam.
"In our neighboring country of the Netherlands, this already works very well," Brenner reports. People are sent an individual invitation to participate in the program and the test is directly sent with the letter. This approach achieves participation rates of more than 60 percent. Germany is presently a far cry from that.
Anton Gies, Katarina Cuk, Petra Schrotz-King, Hermann Brenner: Direct Comparison of Diagnostic Performance of 9 Quantitative Fecal Immunochemical Tests for Colorectal Cancer Screening. Gastroenteroloy 2017. DOI: 10.1053/j.gastro.2017.09.018
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Caption: Colon cancer under the microscope
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