Different kinds of markers
Some markers support diagnosis, some carry prognostic information, and some are predictive — they relate to the likelihood of benefit from a specific treatment approach.
Distinguishing between these roles is important, because they answer different questions.
Interpretation in context
A marker rarely stands alone. Its meaning depends on cancer type, stage, prior treatment and the assay used.
This is why biomarker results are discussed in clinical context rather than read as instructions.