Cancer biomarkers are measurable substances, genes, proteins, or molecular changes that can provide information about cancer presence, tumour type, prognosis, treatment selection, or response to treatment.
Common tumour biomarkers
- AFP: Hepatocellular carcinoma and yolk-sac tumours.
- CEA: Mainly colorectal cancer; also associated with gastric, pancreatic and breast cancers. Useful mainly for monitoring.
- CA 19-9: Pancreatic and biliary tract cancers; mainly used for monitoring.
- CA-125: Epithelial ovarian cancer; useful in monitoring and selected diagnostic evaluation.
- CA 15-3: Breast cancer; mainly used for monitoring advanced disease.
- PSA: Prostate cancer; used alongside clinical assessment and other investigations.
- β-hCG: Gestational trophoblastic disease and germ-cell tumours; useful for diagnosis and monitoring.
- Calcitonin: Medullary thyroid carcinoma.
- Thyroglobulin: Monitoring differentiated thyroid cancer after treatment.
- LDH: May reflect tumour burden and has prognostic value in several malignancies, including lymphoma and germ-cell tumours.
Important molecular biomarkers
- HER2: Breast and gastric cancers; identifies patients who may benefit from anti-HER2 therapy.
- EGFR mutations: Non-small-cell lung cancer; can guide targeted therapy.
- ALK rearrangement: NSCLC; targetable with ALK inhibitors.
- ROS1 rearrangement: NSCLC; potentially targetable.
- BRAF V600E: Melanoma and several other cancers; may guide targeted treatment.
- KRAS/NRAS: Colorectal cancer; important in selecting anti-EGFR therapy.
- BRCA1/BRCA2: Breast, ovarian, pancreatic and prostate cancers; may identify candidates for PARP inhibitors.
- PD-L1: Helps determine eligibility for certain immunotherapies.
- MSI-H/dMMR: Important predictive biomarker for immune-checkpoint inhibitor therapy and may indicate hereditary cancer risk.
- NTRK fusions: Rare alterations that can be treated with TRK-targeted therapy.
Clinical pearl
A raised tumour marker does not automatically mean cancer. Many markers can increase because of benign diseases, inflammation, pregnancy or other conditions.
Therefore, cancer biomarkers should generally be interpreted together with history and examination, imaging, histopathology and other laboratory investigations.
