In head and neck squamous cell carcinoma (HNSCC) patients, the use of drugs acting against the epidermal growth factor receptor (EGFR), has shown to be beneficial in curative and palliative settings.Treating HNSCC patients through biomarkers able to predict response and linked to the biol. effect of treatments should be advisable, but no biomarkers other than PD-L1 expression have entered into clin. practice so far.The aim of these studies is the evaluation of the biol. activity, which is variously defined according to the drug under study.Our aims were to assess the post-treatment variations of available models/signatures predictive of EGFR inhibitor response and their modifications in relation to the microenvironment.Gene-expression based biomarkers in pre-treatment samples.Considering the hypoxia tumor properties, a significant inverse correlation between ΔSUV and Cl3 or BA models was observed in both CET and AFA studies (i.e. high hypoxia GE scores were associated with better response), while the inverse correlation was less consistent once the three signatures (i.e. Winter, Buffa, Eustace) were applied.When tumor microenvironment is assessed, only AFA treatment disclosed a significant pos. correlation between ΔSUV and immune score or IFNγ signature (i.e. low immune scores were associated with better response).Exploring the integrated relationships among ΔSUV, hypoxia models and immune score in a primarily sequential 3D structure, a significant inverse correlation between hypoxia and immune score was found to be correlated to ΔSUV (Fig. 1C).This means that a deep clin. response was associated with higher hypoxia and low immune score.Biomarkers expression changes after neoadjuvant EGFR inhibitors treatment.The association of hypoxia and immune score and the response to both EGFR inhibitors was evidenced in post- compared to the pre-treatment specimens (Fig. 1D reports the association between the decrease in Cl3 model and the increase in immune score).On the contrary, the predictive role of IFNγ was not confirmed in AFA pre- post- treatment samples.To our knowledge, the present work reports the first anal. of the inverse correlation between hypoxia and immune score with respect to the clin. activity of EGFR-inhibitors in HNSCC, suggesting a predictive role.These results seem to indicate that the use of anti-EGFR and immune checkpoint inhibitors (ICI), either in combination or in sequence, could sensitize to ICI the hypoxic cancers that are less sensitive to immunotherapy. Further studies are needed to confirm this hypothesis.