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

Abstract

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. Methods: 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. Results: 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. Conclusion: 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.

Keywords: CHAARTED; Oncology: GU; PET; PET/CT; PSMA; mHSPC; metastasis-directed treatment; prostate cancer.

Graphical abstract

FIGURE 1.

mHSPC disease extent as stratified by CT using CHAARTED criteria and PET using tumor volume and miTNM. Criteria for combined (miTNM and volume) PET volume-of-disease assessment are shown. Dashed line indicates area under curve for approximate 40-cm³ cutoff between PET LVD and PET HVD. Three-year overall survival is given for 40 patients (0 = alive; † = died; all others alive and 3 y after PET not yet reached). diss = disseminated; oligo = oligometastatic; uni = unifocal.