Incidence of mastoiditis in nasopharyngeal carcinoma following anti-PD-1 therapy: A propensity-matched analysis

Mastoiditis can be induced by radiotherapy and is closely associated with hearing loss. This study aimed to investigate the incidence of mastoiditis in patients with locally advanced nasopharyngeal carcinoma (LANPC) undergoing anti-programmed death 1 (PD-1) therapy. We retrospectively reviewed patients with primary locoregionally advanced nasopharyngeal carcinoma who received intensity-modulated radiotherapy and concurrent cisplatin-based chemotherapy with or without anti-PD-1 therapy from January 2020 to January 2022 in a single medical institution. Group A received neoadjuvant chemotherapy (NACT) + concurrent chemoradiotherapy (CCRT) + anti-PD-1 therapy, whereas Group B received the same treatment, except for anti-PD-1 therapy. We employed a propensity score matching method to match patients from each group in a 1:1 ratio. The severity of mastoiditis was assessed using magnetic resonance imaging, specifically grading mastoid opacification on a scale of 0 – 3. A total of 136 out of 259 eligible patients were propensity-matched, with 68 patients in Group A and 68 patients in Group B. No significant differences were observed in patient and tumor characteristics between the two groups. There were no significant differences in the incidence rates of severe mastoiditis between the two groups before NACT, before CCRT, at 0 months, and at 3 months following CCRT. However, the incidence rate of severe mastoiditis at 6 months following CCRT was significantly higher in Group A compared to Group B (35.3% vs. 20.6%, P = 0.008). Analysis of variance with repeated measures demonstrated that anti-PD-1 therapy did not increase the incidence rate of severe mastoiditis in LANPC patients compared to immunotherapy-free patients following CCRT (P = 0.24). LANPC patients receiving anti-PD-1 therapy did not significantly experience more severe mastoiditis during CCRT, but there was an increasing trend post-CCRT. Additional follow-up with a larger patient cohort is necessary to draw definitive conclusions.