Box 1.

What is a biomarker?

A biomarker is a ‘characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention’.3 Biochemical biomarkers may be detected in patient samples such as blood urine or tissue biopsies and are particularly useful in oncology if the marker is exclusively present or absent in malignant cells compared with normal cells, or if there is a significant difference in production, secretion, or accumulation compared with normal tissue. Prostate cancer-associated biomarkers may be useful for:  • Screening and/or diagnosis  • Clinical staging  • Estimating prognosis  • Predicting response to treatment  • Monitoring the response to treatment  • Detecting recurrence  • As potential therapeutic targets