Influence of COVID-19 Vaccination on Treatment-Related Adverse Events and Oncologic Outcomes of Non-metastatic Nasopharyngeal Carcinoma

Background: The influence of COVID-19 vaccination on treatment of non-metastatic nasopharyngeal carcinoma (NPC) who were newly diagnosed after the widespread vaccination against COVID-19 and subsequently treated withchemoradiotherapy is not known. Methods: We performed a retrospective cohort study, patients in the vaccinated group had received at least one COVID-19 vaccination before chemoradiotherapy and those in the control group had not. Propensity score matching was used to minimize potential selection bias between groups. Primary endpoints were acute and late treatment-relatedadverse events (TRAEs). Secondary endpoints included overall survival (OS), progression-free survival (PFS), distant metastasis-free survival (DMFS), and locoregional relapse-free survival (LRRFS) at 2 years. Results: Our study enrolled 893 patients with newly diagnosed non-metastatic NPC between May 2020 and December 2021. At last follow-up on December 31, 2023, the median follow-up was 31.6 months (interquartile range [IQR], 28 to 35.5 months). On propensity score matching analysis, vaccinated group had higher prevalence of grade-3–4 neutropenia (24.2% vs . 18.0%, P =0.048), grade-1–2 fatigue (41.9% vs . 23.9%, P ＜0.001), grade-1–2 nausea/vomiting (66.7% vs . 58.4%, P =0.026) during induction chemotherapy, and grade-1–2 fatigue (58.4% vs . 43.1%, P ＜0.001) during radiotherapy. No significant differences were observed in OS (97.6% vs . 98.5%, P =0.401), PFS (91.7% vs . 87.9%, P =0.097), DMFS (93.2% vs . 91.4%, P =0.385), or LRRFS (95.3% vs . 94.1%, P =0.494) at 2 years in matched groups. Conclusions: COVID-19 vaccination is associated with higher prevalence of acute TRAEs, while no significant influence is observed on the oncologic outcomes of patients with non-metastatic NPC.