Evaluation of EGFR gene copy number as a predictive biomarker for the efficacy of cetuximab in combination with chemotherapy in the first-line treatment of recurrent and/or metastatic squamous cell carcinoma of the head and neck: EXTREME study

Background: The phase III EXTREME study demonstrated that combining cetuximab with platinum/5-fluorouracil (5-FU) significantly improved overall survival in the first-line treatment of patients with recurrent and/or metastatic squamous cell carcinoma of the head and neck (R/M SCCHN) compared with platinum/5-FU alone. The aim of this investigation was to evaluate elevated tumor EGFR gene copy number as a predictive biomarker in EXTREME study patients. Patients and methods: Dual-color FISH was used to determine absolute and relative EGFR copy number. Models of differing stringencies were used to score and investigate whether increased copy number was predictive for the activity of cetuximab plus platinum/5-FU. Results: Tumors from 312 of 442 patients (71%) were evaluable by FISH and met the criteria for statistical analysis. A moderate increase in EGFR copy number was common, with high-level amplification of the gene occurring in a small fraction of tumors (similar to 11%). Considering each of the models tested, no association of EGFR copy number with overall survival, progression-free survival or best overall response was found for patients treated with cetuximab plus platinum/5-FU. Conclusion: Tumor EGFR copy number is not a predictive biomarker for the efficacy of cetuximab plus platinum/5-FU as first-line therapy for patients with R/M SCCHN.