Impact of EBV positivity on clinical outcomes in nasopharyngeal cancer.

Abstract

e18021 Background: Nasopharyngeal carcinoma (NPC) is a rare malignancy with unique geographical distribution. Epstein Barr virus (EBV) plays a key role in the pathogenesis of NPC, with pre and post-treatment serum EBV DNA level as an established prognostic indicator. However, evidence regarding the impact of the tumor cells’ EBV positivity on clinical outcomes is inconsistent. Methods: After IRB approval, we performed a retrospective chart review on NPC patients aged above 18 years seen at Corewell Health William Beaumont University Hospital between July 2015 and December 2020. The Epstein Barr encoding region in-situ hybridization from the biopsy sample determined EBV positivity. We compared progression-free survival (PFS) and overall survival (OS) based on EBV positivity status. Results: A total of 60 NPC patients were included: 19 were EBV-positive, 20 were EBV-negative, and 21 were EBV-unknown. The median age at diagnosis was 50.7 years, and 58.3 years in EBV-positive and negative groups respectively. Most patients in both groups were male (68.4% vs 65%) and had advanced (stage III or stage IV) disease (84.2% vs 75%). The median follow-up duration was 37.3 months. Median PFS and OS were 41 months and 114 months respectively in EBV-negative patients, while median PFS and OS were not reached in EBV-positive patients. There was no significant difference in PFS (0.944) and OS (0.117) among the EBV-positive and negative groups. Among advanced-stage patients, the median PFS was 33 months and 31 months in EBV-negative and EBV-positive groups, respectively, while median OS was not reached in both groups; the difference in PFS (p = 0.821) and OS (0.240) was statistically non-significant. When compared among patients with EBV-positive, negative, and unknown status, PFS was statistically non-significant (p = 0.347) but there was a statistical difference in OS (0.027). Conclusions: Our analysis suggests that the EBV status of the tumor cells does not predict clinical outcomes (PFS or OS) in NPC patients. Even though the OS trend favored EBV-positive patients overall and among those with advanced disease, it was not statistically significant. A difference in OS was seen when patients with unknown status were included and analyzed together with EBV-positive and negative patients, which raises the question of whether the outcome would be different if the majority of patients with unknown status belonged to either the EBV-positive or negative group. With studies in the literature reporting disparate findings, larger prospective studies are needed to better illustrate the impact of tumor cells' EBV positivity on clinical outcomes in NPC.