What is the difference between prognostic and predictive biomarkers?

• A. Prognostic biomarkers are associated with disease outcome independent of treatment; Predictive biomarkers inform about treatment effect.
• B. Prognostic biomarkers indicate treatment effect; Predictive biomarkers reflect disease outcome independent of therapy.
• C. There is no difference between the two.
• D. Predictive biomarkers identify the tissue of origin.

Answer: (A)

Prognostic versus predictive biomarkers are about different uses of biology in guiding care. A prognostic biomarker provides information on the likely course of the disease regardless of treatment. It reflects how aggressive the disease is and helps estimate outcomes like relapse risk or overall survival, guiding prognosis and surveillance, not a choice of therapy. A predictive biomarker, on the other hand, tells you whether a patient is likely to benefit from a specific therapy. It informs treatment decisions by indicating the likely treatment effect, helping to tailor therapy to those most likely to respond.

Examples help anchor the idea: a marker of tumor aggressiveness or stage that correlates with outcome independent of what treatment is given is prognostic. A marker such as HER2 overexpression predicting response to HER2-targeted therapy is predictive. It's possible for a biomarker to have both roles in different contexts, but conceptually they answer different questions.

The other statements mix these ideas or misstate the purpose: one reverses the relationship between prognosis and treatment effect, another asserts there’s no difference, and another wrongly describes predictive biomarkers as identifying the tissue of origin.