HPV-Positive EBV-Negative Nasopharyngeal Cancer: Prevalence and Impact on Outcomes in a Non-Endemic Population

Purpose/Objective(s): To determine the prevalence of high-risk human papillomavirus (HPV) in non-endemic nasopharyngeal cancer (NPC), its association with p16 status, and potential influence on clinical outcomes in a cohort treated with definitive chemoradiotherapy (CRT). Materials/Methods: We identified 24 patients from a prospectively-maintained database treated with CRT for NPC from 1997 to 2014. All patients had paraffin-embedded tumor specimens on which Epstein-Barr virus-encoded small RNAs (EBER) in-situ hybridization and p16 immunohistochemistry (IHC) were performed. All specimens were then reviewed by an experienced head and neck pathologist who isolated and reverse transcribed total RNA from tumor regions, then performed quantitative PCR for E6 and E7 of 13 different high-risk HPV types. Log-rank tests and Cox proportional hazard models were performed to evaluate the impact of clinical factors on patient outcomes. Survival estimates were derived via the Kaplan Meier method. Results: Of the 24 tumors, 7 were HPV-positive/EBV-negative (29%), 15 were HPV-negative/EBV-positive (63%), and 2 were negative for both HPV and EBV (8%). All tumors positive for HPV mRNA expression were also positive for p16 IHC, and all tumors negative for HPV were also negative for p16, resulting in a 100% sensitivity and 100% specificity of p16 as a surrogate for high-risk HPV expression. Median age of diagnosis was 48 (19 – 68). All but 1 HPV-positive tumor was WHO II and no patients with HPV-positive tumors were WHO III. All patients received concurrent chemotherapy, with 3 patients also receiving neoadjuvant and 16 receiving adjuvant chemotherapy. Median doses to the primary and neck were 70 Gy (69.96 – 72) and 56 Gy (50.4 – 64.6), respectively. Median follow-up was 5.9 years (0.9 – 18.0) and was not different when stratified by HPV status. Local-regional control at 5 years was 100% for HPV-positive versus 81.9% for HPV-negative patients (p=0.171). Distant control at 5 years was 83.3% for HPV-positive versus 70.1% for HPV-negative patients (p=0.414). Overall survival at 5 years was 100% for HPV-positive versus 74.5% for HPV-negative patients (p=0.044). Multivariable analysis revealed that older age (HR 1.15, 95% CI 1.01-1.28) and advanced nodal stage (HR 33, 95% CI 1.19-91.44) remained as independent predictors of OS. Conclusion: We revealed that in a group of patients diagnosed with NPC in the midwest United States, HPV-driven NPC comprised a significant proportion of NPC cases, and was mutually exclusive from EBV positivity. Importantly, we discovered that p16 IHC is a strong surrogate marker for HPV-positivity in NPC. Patients with HPV-positive NPC had significantly improved overall survival in our cohort