Evaluating the role of bone scan in staging intermediate-risk prostate cancer: Insights from ISUP grade groups II and III

Purpose: Prostate cancer (PCa) staging often includes bone scans to detect metastases, particularly in intermediate-risk patients classified under International Society of Urological Pathology (ISUP) grade groups II and III. However, the necessity of routine bone scans in this group remains debated. Limited data exist on this specific objective, especially regarding ISUP grade groups II and III. Our study aims to determine the rate of positive bone scan findings among intermediate-risk PCa patients (ISUP grade groups II and III), identify clinical and pathological predictors of bone metastases, and assess whether routine bone scans are necessary for this population. Material and methods: This retrospective observational study, conducted from 2022 to 2024 at the University Hospitals of Derby and Burton National Health Service Trust, analyzed 400 intermediate-risk PCa patients. Clinical stage, radiological T stage, prostate-specific antigen (PSA) levels, perineural invasion, and ISUP grade were evaluated as potential predictors of bone scan positivity. Logistic regression analysis and receiver operating characteristic curve analysis were used to assess predictive accuracy. Results: Bone scan positivity increases with advancing clinical stages (from 7.8% in cT2b to 28.6% in cT4) and radiologic T stages (0% for T1a/T2a to 50% for T4). In addition, it was found to be significantly related to PSA values, with maximum frequency in patients who had PSA >20 ng/mL (10.1%). ISUP grade also had a significant association, where group III had higher bone scan positivity at 5.8% compared with group II at 1.3%. Receiver operating characteristic analysis revealed an area under the curve of 0.836 (95% confidence interval: 0.729–0.943), which is an excellent discriminatory ability of PSA levels. Conclusion: Clinical stage, radiological T stage, and levels of PSA can be significant predictors of bone scan positivity in the intermediate-risk patient with PCa. These facts suggest that universal routine bone scanning may not always be necessary, and clinical as well as radiological factors might guide their use.