The Multi-Source Cancer System (SMSC) is a government initiative whose development has been entrusted to the InVS. It aims to strengthen the cancer surveillance system based on registries—which only partially cover the national territory—in order to address new challenges in surveillance. Its objectives include routine surveillance, support for investigations in the event of an alert, and the conduct of epidemiological studies. This system relies on cross-referencing three sources of individual data using a unique identifier generated by the CnamTS: the PMSI, the ALD30, and ACP data. The first phase of development involves establishing the national ACP database and the system for anonymizing and transmitting data to the InVS. The second phase involves cross-referencing the three sources to record new cases of cancer. The SMSC will be tested in 2007 for thyroid cancers in two pilot regions. It will involve various partners: the ACPs, the CnamTS, the DRASSs, and Inserm’s IFR69. During this test, the eight participating ACP centers will have access to a specific module developed by the InVS to generate the “thyroid” epidemiological record. If the trial is successful, plans are in place to expand the system for thyroid cancers nationwide and then to other cancers warranting national surveillance (in connection with widespread screening campaigns or those potentially linked to environmental exposure). The expansion of the system will depend on the ability to produce standardized ACP reports, extract the data necessary for surveillance from existing data within specialized software, and involve all pathologists. To achieve this, collaboration between the InVS and the INCa, in close coordination with pathologists, is necessary. (R.A.)