Prognostic value of the inflammatory prognostic index for postoperative recurrence in non-muscle-invasive bladder cancer

Abstract

Abstract Background To evaluate the prognostic value of the inflammatory prognostic index (IPI) for recurrence after transurethral resection of bladder tumour (TURBT) in non-muscle-invasive bladder cancer (NMIBC), and to compare its discriminatory performance with that of the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and lymphocyte-to-monocyte ratio (LMR). Methods This retrospective study included 123 patients who underwent TURBT for primary NMIBC. The primary analysis evaluated IPI as a continuous variable. Optimal cut-off values were determined by receiver operating characteristic (ROC) curve analysis, recurrence-free survival (RFS) was characterised by Kaplan–Meier estimation, and independent predictors were identified by Cox proportional hazards regression. Bootstrap internal validation (B = 1000) was applied to quantify overfitting and assess cut-off stability. Results During a median follow-up of 36 months, 44 patients (35.8%) developed disease recurrence. Among the markers tested, IPI showed the largest area under the curve (AUC = 0.790, 95% CI 0.705–0.874) and performed better than NLR (AUC = 0.613), PLR (AUC = 0.523, 95% CI 0.418–0.629), and LMR (AUC = 0.624). When analysed as a continuous variable, each 0.1‑unit increase in IPI was associated with a 12% higher recurrence risk (HR 1.12, 95% CI 1.07–1.18, P < 0.001). For clinical interpretability, the optimal IPI cut-off was 0.223. In multivariable analysis, IPI ≥ 0.223 (HR 5.574, 95% CI 2.583–12.029, P < 0.001) and diabetes mellitus (HR 2.853, 95% CI 1.279–6.366, P = 0.010) were independently associated with recurrence. IPI remained significant after adjustment for either pathological grade or EAU risk group. A pre‑specified Fine–Gray competing‑risks sensitivity simulation gave similar results, suggesting that the association was not driven by overestimation of recurrence in the presence of hypothetical competing non‑cancer mortality (subdistribution HR 5.91, 95% CI 2.87–12.19; P < 0.001). Bootstrap validation suggested limited overfitting (bias-corrected C-statistic 0.790; optimism 0.020), a stable cut-off (bootstrap median 0.227, 95% CI 0.084–0.617), and good calibration (bias-corrected calibration slope 0.86, Brier score 0.091). Conclusions Preoperative IPI, analysed primarily as a continuous variable, was an independent predictor of recurrence after TURBT in patients with NMIBC, with each 0.1‑unit increase associated with a 12% higher recurrence risk. It showed better discriminatory accuracy than NLR, PLR, and LMR and may be a practical, low‑cost adjunct for risk stratification and individualized postoperative surveillance; the dichotomised threshold reported here is cohort‑specific and requires external validation.