Table 1. Characteristics of an “ideal” biomarker [modified from references (11,12)].

Routinely accessible

Rapidly available (short turn-around time)

Easily quantifiable

Cost-effective

Reproducible

Accurate

Endowed by good sensitivity and specificity

High predictive values

Good correlation with the outcome of interest

Predictor of a key (“hard”) endpoint—ideally, OS

Easy to interpret

Objective

Stable (i.e., kinetic independent of internal or external conditions)

Non (or at least minimally) invasive