BackgroundThe prognostic nutritional index (PNI) integrates both nutritional and immune indicators and provides promising prognostic value for various malignancies. However, there is still no specific consensus relating to the precise relationship between the pretreatment PNI and the survival outcome of patients with prostate cancer (PCa). Here, we performed a meta-analysis to determine the prognostic significance of PNI for patients with PCa.MethodsWe used the PubMed, EMBASE, Web of Science, Cochrane Library (CENTRAL), and CNKI databases to identify and retrieve eligible articles that were published in any language up to the 1st March 2023. Our analysis considered hazard ratios (HRs) and 95% confidence intervals (CIs) published in the included studies. Data synthesis and analysis were conducted using Stata 15.1 software.ResultsA total of ten studies featuring 1631 cases were included in our quantitative analysis. Analysis showed that a low PNI at baseline was significantly associated with poor overall survival (OS) (HR: 2.16; 95% CI: 1.40-3.34; p = 0.01), progression-free survival (PFS) (HR: 2.17; 95% CI 1.63-2.89; p < 0.001). Owing to high levels of heterogeneity, we performed subgroup analysis based on disease staging, sample size, and cutoff value; we found that disease staging may have been the source of the heterogeneity. A low pretreatment PNI was associated with poor survival outcomes for both metastatic castration-resistant prostate cancer (mCRPC) patients and nonmetastatic castration-resistant prostate cancer (nmCRPC) patients.ConclusionsA low pretreatment PNI was significantly correlated with a worse OS and PFS in patients with PCa. A low pretreatment PNI may act as a reliable and effective predictor for the prognosis of patients with PCa. Further well-designed studies should be performed to fully evaluate the prognostic performance of this novel indicator for PCa.