EGFRv3 and PTEN as prognostic markers in head and neck squamous cell carcinoma patients treated with cetuximab.

Abstract

e17032 Background: Cetuximab (CTx) is used in treatment of locally advanced (LAD) head and neck squamous cell carcinoma (HNSCC) in combination with radiotherapy (RT) or in metastatic disease (MD). There is no comparison between CTx plus RT and cisplatin plus RT. Patients treated with CTx in daily clinical practice are frequently different from the selected population treated in clinical trials. There are no biomarkers for efficacy of CTx in HNSCC. EGFR variant 3 mutation (EGFRv3), an extracellular domain mutation of EGFR, has been reported in different frequencies in HNSCC in the last years and its association with prognosis and CTx efficacy is still unknown. Methods: Retrospective review of data from patients with HNSCC treated with CTx at a single institution from 2007 to 2010. We evaluated CTx efficacy and expression of EGFRv3, EGFR, PTEN, CD44 and CD44v6 and their impact in objective response rate (ORR), progression free survival (PFS) and overall survival (OS). Biomarkers were analyzed by immunohistochemistry in tissue microarray. Results: For a median follow-up time of 13 months, 61 patients with LAD treated with RT plus CTx had a median OS of 22.7 months, and a median PFS of 8.0 months. Age adjusted Charlson Comorbidity Index (AA-CCI) and ECOG performance status were the most important predictors of poor prognosis in this population. For a median follow-up time of 10.9 months, 44 patients with MD had a median OS of 13.0 months and a median PFS of 7.0 months, for an ORR of 53.7%. EGFRv3 was expressed in 27.1% of tumor samples and was not associated with any clinical outcome. EGFR positivity was associated to higher ORR in LAD and PTEN negativity was associated with shorter OS in the MD setting. Conclusions: In a non selected population with LAD treatment results with CTx in combination with radiotherapy were worse than expected by the phase III study, median OS 22.7 months vs 49.0 months. This difference may be attributed to different population characteristics with higher ECOG and AA-CCI in our study and warrants an adequate proof of efficacy of CTx in this population. EGFRv3 is present in HNSCC but does not impact prognosis. PTEN and EGFR expression emerged as potential biomarkers in HNSCC patients treated with CTx.