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4065 Background: Cetuximab is a chimeric IgG1 Mab that targets the human epidermal growth factor receptor (EGFR). Most clinical trials using cetuximab in mCRC treated patients (pts) with EGFR positive tumors determined by immunohistochemistry (IHC). The intensity of EGFR immunostaining (IS) has not been related to the activity of cetuximab, and objective responses have been reported in pts with EGFR negative tumors. Potential reasons will be presented. Methods: This phase II multicenter study enrolled pts with refractory EGFR-undetectable mCRC who have received at least 1 standard fluoropyrimidine-containing chemotherapy regimen and an ECOG PSgrade 3: infusion related reaction, hypomagnesaemia, dyspnea and skin rash. Two pts discontinued treatment due to Aes: 1 each with an infusion related reaction (above) and a small bowel obstruction. Efficacy endpoints will also be determined by an independent review. Conclusions: These preliminary results indicate that cetuximab monotherapy is active in refractory mCRC pts with EGFR undetectable disease. This activity is comparable to cetuximab monotherapy in EGFR-detectable, refractory mCRC, confirming that EGFR IHC is an unreliable indicator of cetuximab activity. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration ImClone ImClone ImClone
Wierzbicki et al. (Tue,) studied this question.