Evidence-appraisal glossary
Predictive Biomarker
A predictive biomarker forecasts whether a patient is likely to benefit, or suffer harm, from a specific treatment. It helps choose therapy, unlike a prognostic factor, which only forecasts the general course of disease.
Also called: treatment effect modifier.
A predictive biomarker interacts with treatment: the effect of therapy differs depending on the marker's value, which statistically is treatment effect modification. Establishing one usually requires a trial in which marker-positive and marker-negative patients are both randomized, so the marker by treatment interaction can be measured. Marketing a marker as predictive on the basis of prognostic data alone is a common and costly error.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.