A prognostic biomarker provides information about the patients overall cancer outcome, regardless of therapy, whilst a predictive biomarker gives information about the effect of a therapeutic intervention. A predictive biomarker can be a target for therapy.
REF: PMID 18396036, “Prognostic versus predictive value of biomarkers in oncology”
The term prognostic value refers to a genetic factor’s ability to project the natural history of disease in relation to another factor (such as treatment or environmental exposure or another genetic factor; henceforth referred to as treatment) by discriminating between good versus bad prognosis, thereby providing insights into whom to treat with novel modalities.
The term predictive value refers to a genetic factor’s ability to project the benefit of treatment under a suitable definition of the term benefit [Sawyers 2008; Italiano 2011]. When the magnitude of treatment benefit changes with the level of the genetic factor, a gene-treatment interaction can be included in a relevant statistical model to represent this change.
REF: PMID 26349638, “Prognostic and predictive values and statistical interactions in the era of targeted treatment”