DISTINGUISHING PROGNOSTIC AND TREATMENT-PREDICTIVE IN FORMATION FOR LOCALIZED PROSTATE-CANCER

Objectives. To distinguish the concepts of prognostic and treatment-pr edictive information for localized prostate cancer. Methods. We define d a prognostic factor as one that identifies subgroups associated with differing outcomes in untreated patients. A treatment-predictive fact or identifies patients with differing outcomes as a consequence of tre atment and is best identified in a large, randomized trial. Outside of such a trial, a treatment-predictive factor can be identified in prog nostic subgroups or after adjustment for prognostic factors. Results. The distinctions between prognostic and treatment-predictive factors a re illustrated by hypothetical examples. Conclusions. The practical im plication of the distinctions is that prognostic information may not p rovide reliable treatment-predictive information, that is, additional information may be needed before selection of patients for different t reatments can be based on prognostic information. Determination of the relative treatment effect in any prognostic subgroup of patients requ ires a comparative setting. Until now, identified prognostic factors f or localized prostate cancer at best can give guidance for clinical de cisions on which patients should not be offered local aggressive thera py if the aim of the therapy is to cure the patient of the disease.