[Criteria for evaluating prognostic factors].

In oncology prognostic factors are defined as variables (covariates) with independent influence on outcome. Toxicity and complications of treatment are not considered. The significance and independence of a putative prognostic factor has to be proven by multivariate analysis. The results of prognostic factor analysis differ depending on tumor entity and residual tumor status. Sometimes differences are observed for various endpoints and certain patient subgroups. For identification of prognostic factors a systematic step-wise procedure is recommended. A checklist of important methodological aspects is suggested. The acceptance of new prognostic factors requires a standardized way to determine the factors, adequate evidence of significance and independence and the demonstration of additional prognostic information and its clinical relevance. By integration of multiple prognostic factors the present tumor classification will be extended to prognostic systems.