aim is to recognize and to reduce risks. Population-based registries can also monitor the effects of preventive measures. All population-based central registries in the United States and Canada are members of the North American Association of Central Cancer Registries. This organization acts as a voice for the registries when dealing with national standard-setting organizations, sets standards for digital cancer record transmission, and certifies the registries for the quality of their data, among other functions. Hospital cancer registry Hospital cancer registries aim at the improvement of cancer therapy, improve quality of care, evaluate adherence to guidelines, etc. They also serve as a source for epidemiological studies. Therefore, they have to collect detailed data about diagnosis, therapy, dates of important milestones in treatment, etc. Improvements can be achieved by: comparison of therapy - which therapy is the best for patients with similar characteristics comparison of therapists - which hospital, which physician has the best results under the same conditions (quality management) evaluation of adherence to guidelines evaluation of timeliness of interventions (time to diagnosis, time to iniation of treatment, etc.) and their effect on prognosis support of treatment - registries can improve information about a patient and help to provide an optimal treatment by planning therapies and generating reminders Cooperation Since the data needed by hospital cancer registries usually include those of population-based cancer registries and both use the same classifications, data can be sent from a hospital cancer registry to a population-based registry thus reducing documentation efforts. Important barriers and facilitators in this process include clear rules on data sharing, which in many countries may be problematic. Some hospital and population-based cancer registries report their incidence data to national organizations that aggregate and publish the data, but in many countries the data are not centrally managed. The way in which these data are formatted to be submitted to these organizations are determined by standards released by standard-setting organizations. Edits are run on the data to check for inaccuracies and duplicate cases before being submitted electronically. Different organizations have different standards for data reliability and completeness, and some award certifications based on the adherence to these standards. Registries by country United States SEER Registries The Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute collects and publish data on cancer incidence and survival throughout the United States. The information from population-based cancer registries covers approximately 28 percent of the