In metastatic non-small cell lung cancer, patients with tumours harbouring either EGFR exon 19 or 21 gene mutations or the EML4-ALK fusion protein can be offered oral targeted therapies against EGFR ( gefitinib or erlotinib) or ALK ( crizotinib), respectively, which are more effective than cytotoxic chemotherapy. Another example is expression of the oestrogen receptor in breast cancer, which correlates with sensitivity to hormonal agents used in the adjuvant and metastatic settings.

Approximately 15% to 20% of patients with invasive breast cancer have increased expression of the HER2/neu protein (a member of the EGFR family of transmembrane receptors) that is associated with response to anti-HER2-targeted agents such as trastuzumab, pertuzumab, and trastuzumab-emtansine. An example of a predictive biomarker in breast cancer is expression of the HER2/neu protein. For patients who are biomarker negative, there is no difference in survival between treated and untreated patients. As depicted graphically on the right, the probability of survival depends on treatment in those patients who express the biomarker associated with response to a particular therapy. Patients expressing (C) and not expressing (D) the biomarker of interest.Ī predictive biomarker is usually measured before treatment and provides information on the probability of response to a particular therapy. Predictive biomarkers: Treated (A) and untreated patients (placebo or best supportive care) (B).

Predictive vs prognostic biomarkers