| Summary: | Prakash Peddi,1 Bhavna Paryani,2 Amol Takalkar,2 Paige Bundrick,3 John Ponugupati,4 Binu Nair,5 Hazem El-Osta1 1Department of Medicine, Division of Hematology-Oncology, 2Department of Radiology, 3Department of Head and Neck Surgery, Louisiana State University Health Sciences Center, Shreveport, LA, 4Oncology Department, Herbert J Thomas Memorial Hospital, South Charleston, WV, 5Baylor Scott & White Medical Center - Waxahachie, Waxahachie, TX, USA Background: Metastatic head and neck squamous cell carcinoma (HNSCC) carries a very poor prognosis. A better understanding of the molecular driver of the disease and the identification of biomarkers of response remain paramount for an effective personalized therapy. Case report: We report an original case of a 56-year-old patient diagnosed with metastatic HNSCC to both kidneys, who experienced a long-lasting complete response to a single-agent cetuximab, a monoclonal antibody-targeting EGFR. Comprehensive multiplatform biomarker analysis of the tumor revealed the presence of phosphatidyl-inositol 3 kinase mutation, EGFR overexpression, and the absence of PD-1/PD-L1 expression. Since PI3K, a downstream effector of EGFR, is activated, the tumor regression may have occurred mainly through a cetuximab-induced immune-mediated response, rather than EGFR signal blockade. It is plausible that this effect was enhanced by the lack of PD-1 and PD-L1 expression. Conclusion: Our case proposes that the absence of PD-1 and PD-L1 expression in conjunction with EGFR overexpression may correlate with better response to cetuximab in HNSCC. This hypothesis needs to be examined through a large clinical trial. Keywords: biomarker, cetuximab, EGFR blockade, exceptional response, head and neck squamous cell carcinoma
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