Cancer biomarkers are measurable indicators that provide information about the presence, type or behavior of a tumor. They can be molecules produced directly by cancer cells or by normal cells in response to cancer. These markers appear in blood, urine, other body fluids or tissue and include DNA, RNA, proteins, metabolites and even whole circulating tumor cells.

They are used for several purposes. Diagnostic biomarkers help detect cancer and distinguish between benign and malignant conditions. Prognostic biomarkers predict likely disease course, such as risk of recurrence or metastasis. Predictive biomarkers estimate how well a patient will respond to a specific therapy, guiding treatment choices. Monitoring biomarkers track treatment effectiveness and detect relapse.

Genetic and genomic biomarkers are central in modern oncology. Mutations in genes such as EGFR, KRAS, BRAF, BRCA1 and BRCA2, as well as broader patterns of gene expression or chromosomal alterations, inform both prognosis and targeted therapy selection. Liquid biopsies analyze circulating tumor DNA or cells in blood, allowing minimally invasive, repeated assessment of a tumor’s evolving genetic profile.

Proteomic and metabolomic biomarkers examine patterns of proteins or metabolites, capturing functional changes in cancer cells and their environment. Immune biomarkers, such as PD L1 levels or tumor mutational burden, help identify patients who may benefit from immunotherapy.

Despite their promise, many biomarkers face challenges related to sensitivity, specificity, standardization and validation across diverse populations. Current research focuses on panels of multiple biomarkers, integration with imaging and clinical data, and the use of artificial intelligence to improve early detection, personalization of therapy and long term disease management.