Background: 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 2^nd 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 sample size was designed to identify biomarkers associated with a 20% difference between the study arms. Results: 61 patients were included (A: 41/NT: 20). 2 patients in the NT arm were not analyzed (consent withdrawal, no surgery). 7 patients in arm A received < 14d of treatment, including 6 patients with unacceptable toxicity. Afatinib-related toxicities were: grade (G)1 37%, G2 41%, G3 7%, G4 5%, and G5 0%. G≥3 toxicities were mainly gastrointestinal. Partial responses (RECIST1.1) were observed in 3 patients (7.3%) in arm A versus none in the NT arm (p = 0.018). Progressive disease was not observed in arm A versus 3 (16.6%) in the NT arm. Partial responses on PET CT scan by PERCIST were observed in 15/31 evaluable patients (48%) in arm A versus 1/15 (6.7%) in the NT arm (p = 0.005). Conclusions: Afatinib given to HNSCC patients in the preoperative setting is safe and is associated with improved response according to RECIST1.1 and PERCIST compared to no treatment. Clinical trial information: NCT01415674