From DRG databases to an epidemiological observatory for colorectal cancer in a French small area oncology network.

Following a request from the local health authority, we have organised the permanent linkage of DRG/MBDS databases from different tertiary care hospitals from Saint-Etienne urban area. To made anonymous the MBDS, we used the asymmetric hashing and encrypting software developed and registered by the University hospital of Dijon. In each hospital, the selection of acute care stay MBDS is performed on the presence of at least one malignant tumour ICD code. The output is an anonymous but personal 20,000 patients register. We are presenting the method to estimate the incidence of colorectal cancer (CRC) cured between 1996 and 2000 from DRG databases of four hospitals and checking the validity against the figures coming from a cancer registry. Among the 1953 CRC patients observed, 156 patients have followed a CRC surgical excising in 1999. The DRG activity of the 4 observatory hospitals is 33.5% of the total hospital activity for people of the area recorded by the 1999 regional DRG PMSI data bases. The estimation of the incidence is 465 for 1999, the estimation of the same incidence by applying the incidence rate by sex and age from the Isere cancer register to the population of the Loire area, is 504. The under estimation is 7.7% with the observatory method. It is rather difficult to check an estimation by another estimation but in France the evaluation of oncology care strategies is impeded by the lack of cancer registries. The conclusion of this study is a good feasibility and acceptability of the linking procedure when used with a clear healthcare goal. The use of DRG data bases within an oncology network by linking the mandatory MBDS data bases gives the opportunity to share some clinical data between healthcare professionals.