Low HPV16 E6 Seroprevalence in HNSCC: A Prospective Study in Brazil.

Background/Objectives: Head and neck squamous cell carcinoma (HNSCC) remains a global public health challenge with significant morbidity and mortality. Emerging epidemiological data indicate a rising global incidence of human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC). Serology for early HPV antigens has been highlighted as a relevant biomarker for HPV-associated OPSCC. This study aimed to determine the seroprevalence of HPV16 E6 antibodies in HNSCC patients in the state of Espírito Santo, Brazil. Methods: This is a prospective longitudinal cohort study in which 287 patients with HNSCC were enrolled, recruited from two oncology centers in Espírito Santo between 2011 and 2018, along with 68 cancer-free individuals. Serum samples were analyzed using the HPV16 E6 GST Capture ELISA assay. Statistical analysis was performed using SPSS. Binary logistic regression was employed to identify independent predictors of seropositivity. Results: The overall seroprevalence of HPV16 E6 antibodies was 7.3%. Seropositivity was observed in tumors of the oral cavity (6.2%) and oropharynx (13.3%). Patients with OPSCC demonstrated a significantly higher likelihood of seropositivity compared to those with tumors of the oral cavity, larynx, and hypopharynx (OR = 2.96, 95% CI: 1.21-7.28, p = 0.018). The highest frequency of HPV16 E6-positive cases occurred in tumors of the palatine tonsils (OR = 6.00; 95% CI: 1.58-22.89; p < 0.009). No seropositive cases were observed in hypopharyngeal or laryngeal tumors. Among patients with OPSCC and oral cavity squamous cell carcinoma (OCSCC), HPV16 E6 serostatus did not significantly correlate with sociodemographic, behavioral, or clinical tumor characteristics. Conclusions: Our findings reinforce the predilection of HPV-associated carcinogenesis for the oropharynx, more specifically in the palatine tonsils. In addition, this study highlights HPV16 E6 serology as a potential biomarker for HPV-driven OPSCC and underscores Brazil's epidemiological heterogeneity, warranting standardized clinical validation.