Recognizing and managing toxicities of molecular targeted therapies for colorectal cancer

Traditional therapeutic concepts and treatment regimens for colorectal cancer are currently changing with the demonstration of the efficacy of biologic agents in this disease setting. The addition of the anti-vascular endothelial growth factor (VEGF) monoclonal antibody bevacizumab (Avastin) to conventional chemotherapy in the first- and second-line settings has shown a survival benefit; this outcome has helped to rapidly change the standard of care. Other targeted agents, such as anti-epidermal growth factor receptor (EGFR) antibodies, have shown proof of efficacy in colorectal cancer as well. The molecular targeted therapies are associated with toxicity profiles that are distinctly different from those seen with conventional chemotherapy. A notable difference is the absence of high risk for myelosuppression, diarrhea, or alopecia, which are common side effects of cytotoxic chemotherapy. This article will explore the toxicities associated with targeted therapies in detail in an attempt to provide assistance to the practicing oncologist in detecting and managing these side effects in their patients. In particular, the article will focus on the side effects associated with the three currently approved targeted drugs: the anti- VEGF monoclonal antibody bevacizumab and the anti-EGFR monoclonal antibodies cetuximab (Erbitux) and panitumumab (Vectibix).