6021Background: Afatinib, a pan-HER irreversible tyrosine kinase inhibitor, demonstrated limited antitumor activity compared to methotrexate in unselected recurrent and/or metastatic HNSCC patients (LUX-HN1, Machiels et al, Lancet Oncol 2015). The UNICANCER (GEP 11) PREDICTOR study’s objective was to identify predictive and pharmacodynamic biomarkers of biological activity and efficacy of afatinib (EUDRACT N° 2010-024046-29). Methods: This open-label, randomized, multicentric, controlled, phase II study included untreated patients with operable T2-4N0-2M0 HNSCC of the oral cavity, pharynx and larynx, with a PS < 2, adequate organ function and LVEF > 50%. Patients were randomized (2:1) to: oral afatinib (A) 40mg/day (d) for 14-28d or no treatment (NT). Patients had pre-treatment tumor biopsies, tumor imaging, and PET CT scan, with a 2nd tumor imaging before surgery and a PET scan at D15. Adverse events were classified by NCI CTCAE criteria. Based on the biological primary endpoint of tumor reduction the sa...