The prognostic significance of preoperative platelet-to-lymphocyte ratio and interleukin-6 level in non-muscle invasive bladder cancer

Background Non-muscle invasive bladder cancer (NMIBC) is the most prevalent type of bladder cancer, typically associated with a favorable prognosis and a risk of recurrence during the follow-up period. Inflammatory markers have been used to predict prognosis in various cancer types. The aim of this study was to explore the prognostic value of the readily accessible inflammatory markers, platelet-to-lymphocyte ratio (PLR) and interleukin-6 (IL-6), in NMIBC. Methods The study comprised a retrospective analysis of clinical data collected from NMIBC patients diagnosed between October 2018 and October 2020. PLR was calculated using the routine preoperative blood test results, and preoperative IL-6 levels were recorded. Receiver operating characteristic (ROC) curves were generated for PLR and IL-6 level and the optimal cut-off values were determined using Youden's index. Survival curves were generated to evaluate the association between PLR and IL-6, and recurrence-free survival (RFS), and univariate and multivariate analysis were performed using the Cox proportional hazards regression model. A nomogram and calibration curve were generated to assess the clinical significance of the model. Results The ROC curves demonstrated that PLR and IL-6 levels were significantly associated with tumor pathology grade, with area under the curve (AUC) values of 0.833 (95% CI 0.757, 0.910) for PLR and 0.724 (95% CI 0.622, 0.825) for IL-6 levels. PLR and IL-6 levels were also positively associated with tumor recurrence, with AUC values of 0.647 (95% CI 0.538, 0.756) and 0.846 (95% CI 0.769, 0.924), respectively. The survival curves indicated that patients with high PLR and high IL-6 levels had shorter RFS than those with low PLR and low IL-6 level (P < 0.01). Univariate Cox proportional hazards regression analysis showed that age, tumor size, tumor number, pathological grade, PLR and IL-6 were potential risk factors for NMIBC recurrence. Multivariate analysis further revealed that tumor number, smoking, PLR, and IL-6 were independent risk factors for NMIBC recurrence (P < 0.05). Conclusions Preoperative peripheral blood inflammatory markers (PLR and IL-6) are useful predictors of RFS in NMIBC patients at the time of initial diagnosis. High PLR and high IL-6 were identified as independent risk factors for tumor recurrence and could serve as potential biological markers for prediction of NMIBC recurrence.