Validation, revision and extension of the follicular lymphoma international prognostic index (FLIPI) in a population-based setting

Background: The aim of this study was to validate the Follicular Lymphoma International Prognostic Index (FLIPI) in a population-based cohort and to study the relevance of revision and extension of the FLIPI. Patients and methods: Data of 353 unselected patients, 1993-2002, in the Eindhoven Cancer Registry, were collected. Follow-up was completed up to 1 January 2006. Multiple imputations for missing covariates were used. Validity was assessed by comparing observed to predicted survival of the original model and of a revised model with other prognostic variables. Results: The original FLIPI stratified our cohort into three different risk groups based on stage, Hb, lactate dehydrogenase, nodal involvement and age. The discrimination between risk groups was not as good as in the original cohort. A model including age in three categories (≤60/ 61-70/>70 years) and presence of cardiovascular disease (CVD) (yes/ no) resulted in a better prognostic index. The 5-year overall survival rates were 79%, 59% and 28% in the low-, intermediate- and high-risk groups for the extended FLIPI compared with 81%, 66% and 47% for the original FLIPI, respectively. Conclusions: The performance of the FLIPIwas validated in a population-based setting, but could significantly be improved by a more refined coding of age and by including the presence of CVD.