ABSTRACT
Introduction A prognostic factor or test is any measurement available at the time of diagnosis that correlates with disease-free or overall survival in absence of therapy and correlates with the natural history of the disease. It serves as a variable that can explain some of the heterogeneity associated with the expected course and outcome of a disease. This is in contrast to a predictive factor, i.e., any measurement predicting treatment outcome to a given therapy. A prognostic marker should be readily accessible and tested with a uniformly available technology, have a standardized methodology, and be reproducible and independent from other known prognostic markers. It should predict a wide range of clinical outcomes and be validated prospectively in an independent patient population treated with the current standard of care. Prognostic factors may be linked to patient-or tumor-related characteristics. They vary among different patient populations and tumor types and whereas some factors are prognostic for most cancer patients (e.g., performance status, TNM classification), specific prognostic factors may be present. For several tumor types, prognostic indices or nomograms have been developed that may predict the prognosis of patients and be used for patient stratification in studies or treatment selection. Treatment strategies are dependent on prognostic factors that involve the patient, the tumor, and the environment as it relates to the opportunities for early treatment and follow-up care. Newer and more specific prognostic factors dealing with molecular diagnostic studies are being introduced into
evaluation and treatment strategies in daily clinical practice, but they should be validated by standard evidence-based methods.
