There already exists several documentation systems for cancer patients. On of those is the Gießener Tumordokumentationssystem (GTDS). This system is developed and maintained by Dr.med. Udo Altmann since 1991. It is used in over 40 institutions in Germany. Besides the documentation of the procedures, the GTDS offers more functionalitites, like statistical analysis, interfaces to HL7 and more. The original system is a desktop application based on a client-server architecture. Since it is implemented with an old proprietary technology, which is no longer supported, maintainance and extensibility is nearly impossible.