To explore the prognostic factors of muscle-invasive bladder cancer (MIBC) patients, and develop a nomogram model based on tumor biological characteristics, skeletal muscle index and nutritional parameters, which may help surgeons to accurately predict clinical outcomes and make treatment decisions.

The clinical data of 302 MIBC patients who underwent radical cystectomy at the Department of Urology in Qiqihar First Hospital from January 2017 to December 2020 were retrospectively analyzed. The study population was randomly divided into the training group (n=202) and validation group (n=100). The univariate and multivariate Cox regression analysis were conducted to determine the predictors of overall survival (OS) for MIBC patients, and then a nomogram model was established. The predictive performance of the nomogram was evaluated by the consistency index (C-index) and receiver operation characteristic (ROC) curves, and calibration curves were plotted to evaluate its predictive accuracy.

The data of univariate and multivariate Cox analysis indicated that cT stage (cT₃ stage: HR=2.175, 95%CI: 1.467-3.224, P<0.001; cT₄ stage: HR=3.433, 95%CI: 2.020-5.834, P<0.001), lymph node metastasis (HR=2.581, 95%CI: 1.794-3.712, P<0.001), lymphovascular invasion (HR=1.715, 95%CI: 1.184-2.484, P=0.042), skeletal muscle index (HR=0.960, 95%CI: 0.937-0.983, P=0.001) and controlling nutritional status (HR=1.175, 95%CI: 1.099-1.256, P<0.001) were independent prognostic factors for MIBC patients. A nomogram was developed according to the above five variables, with a C-index of 0.762 (95%CI: 0.711-0.798). The ROC curves showed that the area under curve (AUC) values of the nomogram for 1, 2, and 3 year survival prediction were 0.773, 0.887, and 0.876, respectively. The calibration curves showed a good consistency between the predicted probability and the actual observation. In addition, the predictive value of the nomogram model was further validated by an internal cohort. Its C-index was 0.744 (95%CI: 0.702-0.787), and the AUC values for 1, 2, and 3 year survival prediction were 0.793, 0.840, and 0.833, respectively.

The nomogram based on tumor biological characteristics, skeletal muscle index and nutritional parameters provides a simple and effective tool to accurately predict the survival outcome, and it might be helpful to optimize the clinical management of MIBC patients.