Inhibitors of epidermal growth factor receptor and colorectal cancer

: Colorectal cancers (CRC) express the epidermal growth factor receptor (EGF-R), a type I transmembrane receptor with tyrosine kinase activity. EGF-R signaling inhibition is a promising target for cancer therapy. ZD1839 (Iressa, AstraZeneca) and OSI-774 (Tarceva, Roche) are small molecular weight molecules with selective and reversible tyrosine kinase inhibition properties directed to EGF-R. Orally administered, these molecules induce sustained tumor stabilizations in previously treated metastatic CRC patients. The most frequent treatment-related toxicities are fatigue, diarrhea and acne-like follicular rash. The addition in the clinic of 5-FU, lOHP or CPT-11 to ZD1839 or OSI-774 does not seem to increase the own toxicity of each cytotoxic agents. Cetuximab (Erbitux, Merck) is an intravenously administered humanized monoclonal antibody which bind with high affinity with the extracellular domain of the EGF-R. The most frequent treatment-related toxicities are diarrhea, fatigue, nausea and cutaneous toxicity (allergic or acne-like follicular rashes, folliculitis). Most, if not all of these adverse events are mild. Partial responses were observed with cetuximab either alone (RR: 10%) or in combination with CPT-11 (RR: 22%) in patients with CPT-11 refractory advanced CRC which expressed EGF-R. The combination of cetuximab to folinic acid, 5-FU and CPT-11 seems tolerable at the cost of a slight increase of severe diarrhea and neutropenia. Finally, the promising activity of these EGF-R inhibitors has to be confirmed throughout randomized studies.