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What is a biomarker?

Cancer biomarkers

A biomarker is a biological characteristic that can be measured. It indicates a body function, a characteristic of a disease or the activity of a medicine. A cancer biomarker may be a substance secreted by a tumour or a particular response the body exhibits in the presence of cancer. Genetic, epigenetic, proteomic, glycomic and imaging biomarkers can be employed to diagnose cancer and offer prognoses and the epidemiology of a cancer.

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A biological sample (eg blood or serum) from the patient is tested for presence of the biomarker and the results help the doctor to discuss the patient's disease characteristics and potential treatment options.

Biomarkers can be used to:
  • Identify a person’s risk of developing a cancer
  • Provide information about the diagnosis or the characteristics of the cancer
  • Provide information to help treatment decisions
  • Follow the development of the cancer

Increasingly, biomarkers are used to predict health and mortality rates across different demographics.

Some of the non-small cell lung cancer (NSCLC) biomarkers

This is a mutation in a gene called ALK or anaplastic lymphoma kinase. Two genes, known as ALK and EML4 (echinoderm microtubule-associated protein like 4) fuse together to become one abnormal gene that then produces an abnormal protein, tyrosine kinase. ALK is not known to be hereditary. See targeted therapy for ALK-positive lung cancer.

In some cases of NSCLC, changes take place in the BRAF gene, which makes an altered BRAF protein that makes cells grow.

EGFR gene mutation happens when the EGFR signal goes into overdrive, producing abnormal protein tyrosine kinase which causes lung cancers to experience uninhibited growth. In the US, about 15% of lung cancer patients have this mutation. See targeted therapy for EGFR-positive lung cancer.

The KRAS mutation is found in about a quarter of all of patients with NSCLC (mostly adenocarcinoma). This mutation has a high risk of cancer recurrence. KRAS is a biomarker for lung cancer, colon cancer and pancreatic cancer.

MET is also known as a hepatocyte growth factor (HGF) receptor that functions in wound healing and liver regeneration. It also plays an important part in embryonic, neuronal and muscle development. In lung cancer, there may be dysregulation of MET signalling, mutation of the MET gene or amplification of the gene.

PD-L1 (programmed death ligand 1) is an immune checkpoint ligand that slows down or stops T cell activity by binding to the PD-1 receptor in a cancerous environment. PD-L1 can also be found on tumor cells of many types of different cancers, from lung cancer to melanoma.

This is a receptor tyrosine kinase. About 2% of lung tumors have ROS1 fusions and these are more in light smokers and those who have never smoked. ROS1 fusions are also associated with younger age and adenocarcinomas.

References:
National Center for Biotechnology Information:
Biomarkers That Currently Affect Clinical Practice in Lung Cancer: EGFR, ALK, MET, ROS-1, and KRAS.
Retrieved Nov 2017 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4127527/;
VeryWell: ALK Positive Lung Cancer Definition and Treatment.
Retrieved Nov 2017 from https://www.verywell.com/alk-positive-lung-cancer-definition-and-treatment-2248944;
National Cancer Institute: FDA Approves Alectinib for ALK-Positive Non-Small Cell Lung Cancer.
Retrieved Nov 2017 from https://www.cancer.gov/news-events/cancer-currents-blog/2016/fda-alectinib-nsclc;
My Onco: Immunotherapy: PD-L1 Expression.
Retrieved Nov 2017 from https://www.myonco.be/immuno/hcp/about-immuno/immuno-therapy/PD-L1-expression;
Patel SP, Kurzrock R. PD-L1 expression as a predictive biomarker in cancer immunotherapy.
Molecular Cancer Therapeutics. 2015;14(4):847─856;
American Association for Cancer Research: Molecular Cancer Therapeutics.
Retrieved Nov 2017 from http://mct.aacrjournals.org/content/16/4/555