Background: Several molecular targeting agents are available and being used in patients with colorectal cancer, and many others are being tested clinically. Methods: The authors review and present the biology and use, including predictive testing, of the agents currently approved for use in colorectal cancer as well as current data on several newer tyrosine kinase inhibitors that are undergoing clinical trials. Results: The angiogenesis inhibitor bevacizumab and the two EGFR inhibitors cetuximab and panitumumab are currently the three targeted agents approved in colorectal cancer. Recent studies show that the combined use of bevacizumab and EGFR inhibitors may lead to increased toxicity and inferior outcome. Much remains to be understood regarding these drugs and other targeted therapies as well as the underlying mechanism of tumor resistance or responsiveness to treatment. Their optimal use and sequencing with other treatment modalities such as surgery need to be further refined. Conclusions: There is a crucial need for identification of predictive markers of response and identification of possible negative interactions between targeted agents so that we can better select patients likely to respond to treatment.
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