Development of a preliminary nomogram to predict progression of bone scan for castration-resistant prostate cancer

The optimal time to perform bone scan to detect new metastasis during the castration-resistant prostate cancer (CRPC) stage remains undefined. This study attempted to identify predictors of progression of bone scan for CRPC, and use such information to develop a nomogram to predict the optimal time of examinations for bone scan. The analysis included 167 CRPC patients. Progression of bone lesion, as evaluated by bone scan, occurred in 64 (38.3%) cases. A logistic regression identified the following three risk factors: short time to prostate-specific antigen (PSA) progression, severe pain, and short PSA doubling time (PSADT) (P<0.05 for all). A nomogram model was constructed to predict progression of bone scan using time to PSA progression and severe pain as dichotomized variables and PSADT as a continuous variable. The result indicated that a predictive nomogram model showed a bootstrap-corrected concordance index of 0.762 and good calibration using the three readily available variables, and there were worse prognosis and higher progression rate of bone scan for patients with time to PSA progression <6.6 months, severe pain, and short PSADT (<2 months). In conclusion, short time to PSA progression, severe pain, and short PSADT are three risk factors of progression of bone scan for CRPC patients. The predictive nomogram model may be a valuable numerical assessment tool for patient consultation and treatment decision.