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Medline ® Abstract for Reference 67

of 'Systemic chemotherapy for nonoperable metastatic colorectal cancer: Treatment recommendations'

Molecular mechanisms of resistance to cetuximab and panitumumab in colorectal cancer.
Bardelli A, Siena S
J Clin Oncol. 2010;28(7):1254. Epub 2010 Jan 25.
Personalized cancer medicine based on the genetic milieu of individual colorectal tumors has long been postulated, but until recently this concept was not supported by clinical evidence. The advent of the epidermal growth factor receptor (EGFR) -targeted monoclonal antibodies cetuximab and panitumumab has paved the way to the individualized treatment of metastatic colorectal cancer (mCRC). Here we discuss the evidence that mCRCs respond differently to EGFR-targeted agents and that the tumor-specific response has a genetic basis. We outline how, from the initial observation that cetuximab or panitumumab as monotherapy is effective only in 10% to 20% of mCRCs, knowledge has being gained on the molecular mechanisms underlying primary resistance to these agents. The role of oncogenic activation of EGFR downstream effectors such as KRAS, BRAF, PIK3CA, and PTEN on response to therapy is discussed. We suggest that CRCs lacking oncogenic alterations in these four genes have the highest probability of response to anti-EGFR therapies and are defined as "quadruple negative." The rapid and effective translation of these findings into predictive biomarkers to couple EGFR-targeted antibodies to the patients who benefit from them is presented as a paradigm of modern clinical oncology. Finally, unresolved questions such as understanding the molecularbasis of response as well the mechanisms of secondary resistance are presented as the future fundamental goals in this research field.
Laboratory of Molecular Genetics, Institute for Cancer Research and Treatment, University of Torino, Medical School, Str prov 142 Km 3.95, 10060 Candiolo, Italy. a.bardelli@ircc.it