Low prognostic nutritional index is associated with poor outcome in middle-aged and elderly patients with non-metastatic nasopharyngeal carcinoma: a retrospective cohort study

Background Prognostic nutritional index (PNI) and age are effective prognostic factors for patients with non-metastatic nasopharyngeal carcinoma (NPC), and an interaction between them may exist. However, the age cutoff value is generally set at 45 years in current studies. The clinical implications of PNI in middle-aged and elderly patients are unclear. Therefore, we aimed to uncover this issue. Patients and methods We retrospectively collected data from 132 middle-aged and elderly (≥ 45 years old) patients with non-metastatic NPC. The association between covariates and the PNI was analyzed using 2 or t -test. The effect of PNI on the prognosis was evaluated using univariate and multivariate Cox regression analyses. Unadjusted and multivariate-adjusted models were applied. Stratified and interactive analyses were performed to investigate the potential source of heterogeneity. Results Median age (61.0 years versus 59.5 years) and the proportion of patients aged ≥ 60 years (57.6% versus 50.0%) in the low-PNI group were higher than those in the high-PNI group ( P > 0.05). The patients with a low PNI had shorter overall survival (OS) (hazard ratio (HR) = 0.86, 95% confidence interval (CI) = 0.80–0.93; P < 0.001) and progression-free survival (PFS) (HR = 0.93, 95% CI = 0.87–0.99; P = 0.034). The results remained stable after three adjusted models of covariates, including age ( P < 0.05). No significant interactions were observed in middle-aged (45–59 years) and elderly (≥ 60 years) subgroups for OS and PFS ( P for interaction > 0.05). Conclusion Although there is an interaction between PNI and age, PNI is an independent prognostic factor in middle-aged and elderly patients with non-metastatic NPC.