title: Companion biomarkers: paving the pathway to personalized treatment for cancer.
abstract: BACKGROUND
  Companion biomarkers are biomarkers that are used in combination with specific therapies and that prospectively help predict likely response or severe toxicity. In this article we review the role of companion biomarkers in guiding treatment in patients with cancer.
  
  
  BACKGROUND
  In addition to the established companion biomarkers such as estrogen receptors and HER2 (human epidermal growth factor receptor 2) in breast cancer, several new companion biomarkers have become available in recent years. These include v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations for the selection of patients with advanced colorectal cancer who are unlikely to benefit from anti-epidermal growth factor receptor antibodies (cetuximab or panitumumab), epidermal growth factor receptor (EGFR) mutations for selecting patients with advanced non-small cell lung cancer (NSCLC) for treatment with tyrosine kinase inhibitors (gefitinib or erlotinib), v-raf murine sarcoma viral oncogene homolog B1 (BRAF) mutations for selecting patients with advanced melanoma for treatment with anti-BRAF agents (vemurafenib and dabrafenib), and anaplastic lymphoma receptor tyrosine kinase (ALK) translocations for identifying patients with NSCLC likely to benefit from crizotinib.
  
  
  CONCLUSIONS
  The availability of companion biomarkers should improve drug efficacy, decrease toxicity, and lead to a more individualized approach to cancer treatment.
authors: UCD School of Medicine and Medical Science, Conway Institute, University College Dublin, Ireland;
authors: Michael J
authors: MJ
authors: Duffy
authors: John
authors: J
authors: Crown
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D047072:Aromatase Inhibitors / Q000627:therapeutic use; D015415:Biomarkers / Q000378:metabolism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics; D006801:Humans; D058990:Molecular Targeted Therapy; D009154:Mutation; D009369:Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D057285:Precision Medicine; D011518:Proto-Oncogene Proteins / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D014178:Translocation, Genetic; D018631:ras Proteins / Q000235:genetics
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D015415:Biomarkers; D066246:ErbB Receptors; D015514:Oncogene Proteins, Fusion; D011518:Proto-Oncogene Proteins; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D018631:ras Proteins; C522504:EML4-ALK fusion protein, human; C117307:KRAS protein, human; C508053:ERBB2 protein, human; C482119:BRAF protein, human