It is conventional wisdom that science requires critical appraisal and that correlation does not imply causality.
In medicine, science also needs the best possible evidence for benefits and risks associated with preventive and curative interventions. With regard to colorectal cancer screening, we have faced this challenge by conducting an extensive and differentiated research program which has been presented in detail elsewhere (for example [1–3]).
The analysis of trends in incidence and mortality, which is cited by Dr. Völzke in a very abbreviated and selective fashion, is just one of many elements of this research program.
Therefore, our statement is based on a differentiated and critical appraisal of the incidence and mortality trends in Germany, which have been discussed against the background of the worldwide evidence on colorectal cancer screening effectiveness.
Dr. Völzke presents the available epidemiological data in extremely misleading way so that it appears as if the screening colonoscopy would at least cause the same number of deaths as it prevents. This incorrect interpretation is the result of very serious errors in reasoning. Yearly mortality rates based on the total population regardless of age are compared with a mortality rate of screening colonoscopy (set by far too high), a procedure which is recommended for and offered once or twice to people age >55 years.
A more appropriate approach yields the following results: With a total population of more than 80 million in Germany, a reduction of colorectal mortality by 6 or 5 deaths per 100 000 cases annually translates into the prevention of more than 4000 colorectal cancer deaths per year. According to data from the German national screening colonoscopy registry, there has been on average one colonoscopy-related death per year in Germany since the introduction of screening colonoscopy. The ratio of potentially prevented and caused deaths is therefore more than 4000:1 and not 1:1.
Footnotes
Conflict of interest statement
The authors of both contributions declare that no conflict of interest exists.
References
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