[Evaluation of organized cancer screening programs: general aspects and current status in Germany]

In the past decades, it has been increasingly recognized that cancer screening is not always or not exclusively beneficial and, in the case of some measures, the negative effects may even outweigh the benefits. This has fundamentally changed the significance and emphasis placed on the evaluation of cancer screening programs. Generally, there is a distinction between an endpoint evaluation, which assesses the effectiveness or risk/benefit ratio, and a process evaluation, which aims to ensure optimum implementation of the program.Prior to the nationwide introduction of a screening measure, proof of effectiveness should ideally be provided by a randomized controlled trial (RCT), in which persons without a screening offer form the control group. From a scientific point of view, this study design is by far the best method to evaluate the endpoint, as it avoids biases that may distort the results in observational studies. RCT evidence on cancer screening measures currently offered by statutory health insurance providers in Germany - if available at all - originates exclusively from other countries.When mammography screening was introduced as the first organized screening program in Germany, comprehensive measures for process evaluation were taken. In April 2013, the legal basis for the transfer of colorectal and cervical cancer screening into organized programs was created. According to the legal provisions, both a process and an endpoint evaluation are planned for the new programs. It remains to be seen how the necessary data flows will be conceptualized and later implemented in practice.