title: Biomarkers predicting clinical outcome of epidermal growth factor receptor-targeted therapy in metastatic colorectal cancer.
abstract: The monoclonal antibodies panitumumab and cetuximab that target the epidermal growth factor receptor (EGFR) have expanded the range of treatment options for metastatic colorectal cancer. Initial evaluation of these agents as monotherapy in patients with EGFR-expressing chemotherapy-refractory tumors yielded response rates of approximately 10%. The realization that detection of positive EGFR expression by immunostaining does not reliably predict clinical outcome of EGFR-targeted treatment has led to an intense search for alternative predictive biomarkers. Oncogenic activation of signaling pathways downstream of the EGFR, such as mutation of KRAS, BRAF, or PIK3CA oncogenes, or inactivation of the PTEN tumor suppressor gene is central to the progression of colorectal cancer. Tumor KRAS mutations, which may be present in 35%-45% of patients with colorectal cancer, have emerged as an important predictive marker of resistance to panitumumab or cetuximab treatment. In addition, among colorectal tumors carrying wild-type KRAS, mutation of BRAF or PIK3CA or loss of PTEN expression may be associated with resistance to EGFR-targeted monoclonal antibody treatment, although these additional biomarkers require further validation before incorporation into clinical practice. Additional knowledge of the molecular basis for sensitivity or resistance to EGFR-targeted monoclonal antibodies will allow the development of new treatment algorithms to identify patients who are most likely to respond to treatment and could also provide rationale for combining therapies to overcome primary resistance. The use of KRAS mutations as a selection biomarker for anti-EGFR monoclonal antibody (eg, panitumumab or cetuximab) treatment is the first major step toward individualized treatment for patients with metastatic colorectal cancer.
authors.affiliation: The Falck Division of Medical Oncology, Ospedale Niguarda Ca' Granda, Piazza Ospedale Maggiore 3, 20162 Milan, Italy. salvatore.siena@ospedaleniguarda.it
authors.forename: Salvatore
authors.initials: S
authors.lastname: Siena
authors.forename: Andrea
authors.initials: A
authors.lastname: Sartore-Bianchi
authors.forename: Federica
authors.initials: F
authors.lastname: Di Nicolantonio
authors.forename: Julia
authors.initials: J
authors.lastname: Balfour
authors.forename: Alberto
authors.initials: A
authors.lastname: Bardelli
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology* / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D000068818:Cetuximab; D058534:Class I Phosphatidylinositol 3-Kinases; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D018572:Disease-Free Survival; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D009154:Mutation / Q000187:drug effects; D009367:Neoplasm Staging; D016017:Odds Ratio; D051059:PTEN Phosphohydrolase / Q000187:drug effects / Q000235:genetics; D000077544:Panitumumab; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000235:genetics; D011237:Predictive Value of Tests; D011518:Proto-Oncogene Proteins / Q000187:drug effects* / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000187:drug effects / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000187:drug effects / Q000235:genetics; D016032:Randomized Controlled Trials as Topic; D012107:Research Design
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D011518:Proto-Oncogene Proteins; D000077544:Panitumumab; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; D066246:ErbB Receptors; D048493:Proto-Oncogene Proteins B-raf; D051059:PTEN Phosphohydrolase; D016283:Proto-Oncogene Proteins p21(ras); D000068818:Cetuximab