PSMA-PET for the assessment of metastatic hormone-sensitive prostate cancer volume of disease.

Conventional imaging low-(LVD) versus high-volume disease (HVD) are associated with survival in metastatic hormone-sensitive prostate cancer (mHSPC) according to CHAARTED and STAMPEDE trials. We propose a compatible quantitative PSMA-PET framework for disease volume assessment in mHSPC. Three PET centers screened their PSMA-PET database for mHSPC patients. CT versus PSMA-PET stage, lesion number, and classification of LVD vs. HVD were determined by one blinded reader; PSMA-positive tumor volume (PSMA-TV) was quantified semi-automatically. 85 CT-based CHAARTED-LVD and 20 CT-based CHAARTED-HVD patients were included. A PSMA-TV of 40 ml was the optimal cutoff between CT-based CHAARTED-LVD (non-unifocal) and HVD (non-M1c) (AUC 0.86). Stratification into PET-LVD (unifocal or oligometastatic/disseminated <40 mL) and PET-HVD (oligometastatic/disseminated ≥~40 mL or M1c) had 13% misalignment with CHAARTED criteria. PSMA-PET criteria with volume quantification deliver comparable LVD/HVD discrimination with additional subgroups for unifocal, oligometastatic and disseminated disease, critical for guidance of targeted or multimodal therapy.