In Reply We thank Shin et al for their letter providing additional valuable information on potential linkable databases or resources in Korea.
Indeed, similar to Taiwan, Sweden, and Denmark, Korea has a wonderful nationwide health insurance (NHI) database, other national resources, and the capacity for cross-linking some of these databases and/or resources for etiologic information, outcomes, and other related research. As in many countries, these resources are developed separately by different agencies or institutions at different time points, so, although they provide viable options for potential linkage (unlike the Surveillance, Epidemiology, and End Results [SEER]-Medicare linkage ready-to-use database), they require additional steps or modifications for linkage for specific research. For example, the sample research database of approximately 1 million records was not linked to the Korean Central Cancer Registry Data until 2014. In the past, insurance claims were used for disease codes, and to use the customized database for research, additional processes and approval, such as a memorandum of understanding in some cases, are needed. Based on additional information provided by Shin et al, it is fair to say that currently it is highly feasible and/or possible to link NHI data to cancer registry and other databases in Korea. We certainly applaud this important effort and hope that functionality of linkage will continue to improve. We also hope projects with linked data sets will become widely popular.