PSMA PET/CT-derived Tumor Volume for Predicting Outcomes in Patients with Metastatic Castration-Resistant Prostate...

Area of Science:

• Oncology
• Radiopharmaceuticals
• Medical Imaging

Background:

• Accurate prediction of treatment response in metastatic castration-resistant prostate cancer (mCRPC) is crucial for guiding lutetium 177 prostate-specific membrane antigen-617 (Lu-PSMA) therapy selection.
• Existing prediction models for Lu-PSMA therapy require validation and potential enhancement for improved patient stratification.

Purpose of the Study:

• To evaluate the added predictive value of total tumor volume (TTV) derived from prostate-specific membrane antigen PET/CT in existing models for Lu-PSMA therapy response.
• To compare the discriminatory ability of TTV against the number of metastases in predicting patient outcomes.

Main Methods:

• External validation of previously developed prediction models using baseline clinical and imaging variables in 168 mCRPC patients treated with Lu-PSMA.
• Re-estimation of prediction models for overall survival (OS), prostate-specific antigen progression-free survival (PSA-PFS), and PSA50 response, incorporating TTV or continuous number of metastases.
• Assessment of model performance using the concordance index (C index).

Main Results:

• Original models showed moderate predictive accuracy (C indexes: OS 0.70, PSA-PFS 0.68, PSA50 0.72).
• Inclusion of TTV significantly improved the prediction model for OS (C index increase of 0.04, P = .002).
• Higher TTV was associated with shorter OS, shorter PSA-PFS, and lower PSA50 response, outperforming the number of metastases as a predictor.

Conclusions:

• Previously established models effectively predict outcomes for mCRPC patients undergoing Lu-PSMA therapy.
• Incorporating TTV into prediction models significantly enhances their discriminatory ability for OS, PSA-PFS, and PSA50 compared to using the number of metastases.
• TTV is a valuable imaging biomarker for predicting treatment response and survival in patients with mCRPC receiving Lu-PSMA therapy.