PSMA-PET Tumor Volume Stratifies Nonmetastatic Castration-resistant Prostate Cancer.

Background

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Objective

Prostate-specific membrane-antigen positron emission tomography (PSMA-PET) detects distant metastases in more than half of patients with increasing prostate-specific antigen despite castrate levels of testosterone and high-risk nonmetastatic disease on conventional imaging. Here, we aim to evaluate prognostic implications of PSMA-PET staging in patients with nonmetastatic castration-resistant prostate cancer (nmCRPC).

Methods

Overall, 514 patients who underwent PSMA-PET for nmCRPC at investigator sites across the world between 2013 and 2022, were retrospectively evaluated in a large, international multi-center PROMISE-PET Registry study. PROMISE metrics and PSMA-PET reports were retrospectively analyzed in accordance with PROMISE V2 criteria. Total tumor volume, PSMA expression score, and molecular imaging metastatic disease (miM1) were analyzed to prognosticate overall survival (OS).

Results

Median follow-up was 4.4 yr (interquartile range 2.9-6.7). Overall, 294 patients (57%) were deceased at last follow-up. PSMA-PET detected metastatic disease in 340 patients (66%), and visceral metastases in 28 patients (5.4%). The optimal cutoff point for tumor volume was identified as 7.8 ml, which significantly stratified the cohort into low- versus high-volume groups. Patients with high-volume disease had worse OS than those with low-volume disease (hazard ratio [HR], 2.47; 95% confidence interval [CI], 2.22-2.71; p < 0.001). Patients with any distant metastases (miM1) on PSMA-PET had significantly shorter OS compared to those without detectable metastatic disease (HR, 1.74; 95% CI, 1.49-2.00; p < 0.001).

Conclusion

Higher tumor volume on PSMA-PET and presence of distant metastases were strongly associated with OS in patients with nmCRPC. PSMA-PET stage and tumor volume should be included in future nmCRPC risk stratification.