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Introduction Nasopharyngeal carcinoma (NPC) is a rare malignancy with unique geographical distribution. It is prevalent in East and Southeast Asia and rare in non-endemic countries like the USA. P16 is a tumor suppressor gene and there are limited studies with inconsistent results describing the association of its positivity in immunohistochemistry and clinical outcomes. In this retrospective study, we compared progression-free survival (PFS) and overall survival (OS) based on p16 positivity in 60 patients with NPC. Materials and methods Patients aged above 18 years and followed between July 2015 and December 2020 were included in the study. P16 positivity was based on the immunohistochemistry of the biopsy sample. We compared PFS and OS among all p16-positive and negative patients, and then among patients with advanced disease (stage III or IV), and between p16-positive, negative, and unknown status patients. Results There were 15 p16-positive, and 28 p16-negative, with a median age of 54.3 years and 55.7 years respectively. Most patients in both groups were male, Caucasian, and had advanced disease (stage III or stage IV). Both median PFS (p=0.838) and OS (p=0.776) were 84 months in the p16-negative group but were not reached during the study period in the p16-positive group. Among advanced-stage patients, the PFS (p=0.873), and OS (p=0.773) of both groups were not statistically significant. P16 status was unknown for 17 patients, and PFS (p=0.785) and OS (p=0.901), when compared among patients with p16-positive, negative, and unknown status, were also statistically non-significant. Discussion and conclusion Our analysis suggests that p16 status does not predict clinical outcomes in NPC patients. Our sample size was limited but is larger than most studies describing this association. With different studies in the literature reporting disparate findings, we recommend larger prospective studies to better illustrate the impact of p16 positivity on clinical outcomes in NPC., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Ghimire et al.)

Circulating tumour DNA (ctDNA) is defined as short DNA sequences shed by tumour cells into the systemic circulation. A promising use of ctDNA includes the detection of minimal residual disease (MRD) and is currently being studied in multiple types of solid tumours. Literature for the use of individualised ctDNA in nasopharyngeal carcinoma (NPC) is not available, although circulating Epstein-Barr virus DNA level is validated as a prognostic factor. We present a man in his 40s diagnosed with stage IV NPC who was started on chemotherapy with cis-platinum and gemcitabine. Serial monitoring of ctDNA completed to aid in detecting MRD after treatment demonstrated initial up-trending values correlating with subsequent imaging findings showing progression. Reinitiation of a different chemotherapy regimen significantly improved the ctDNA level, with corresponding imaging exhibiting a similar response. This case provides insight into the potential use of ctDNA in NPC and the benefit of serial ctDNA monitoring during treatment., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.)