In cancer, most prognostic tests are biomarkers that help indicate likelihood of disease events such as progression of disease, metastasis (spread of cancer), or recurrence. Prognostic markers can also be used to predict which patients will have a very low risk of disease events and can avoid toxic treatment, or high-risk patients who may benefit from more aggressive therapies. While presence or absence of a prognostic marker can be useful to determine which patients need treatment it does not directly predict the response to a treatment.
Biomarkers can be lymph nodes, pathology features, or proteins found in the blood. Recently genetic mutations in tumor cells have also been included with the prognostic tools used in cancer treatment. These tests examine several genes to help determine the likelihood of recurrence and whether that patient should continue chemotherapy.