Florastamin Uptake on PSMA PET/CT as an Imaging Biomarker of Tumor Aggressiveness in Prostate Cancer

Background: This study aimed to evaluate the association between the uptake on F-18 florastamin PET/CT, which targets the prostate-specific membrane antigen (PSMA), and the histopathological grade of the primary tumor in newly diagnosed prostate cancer patients. Methods: As a subset analysis of a phase III multicenter trial of florastamin PET/CT in East Asian men, the data from a single institution of pathologically confirmed prostate cancer cases were reviewed. The maximum standardized uptake value (SUVmax) was measured from the primary tumor on florastamin PET/CT images of 110 participants. The International Society of Urological Pathology (ISUP) grade group obtained from surgery or biopsy was classified into three risk groups: low (ISUP 1), intermediate (ISUP 2–3), or high (ISUP 4–5). Correlation was tested between the SUVmax of the prostate cancer and the ISUP-based risk. The PSA level and Prostate Imaging Reporting and Data System (PIRADS) score from MRI were also assessed for association with the SUVmax and ISUP-based risk. Results: The SUVmax of the primary tumor and the PSA level showed significant positive correlation with the ISUP-based risk (ρ = 0.541, p < 0.001; ρ = 0.328, p = 0.001, respectively). The tumor SUVmax increased with higher PIRADS scores (ρ = 0.516, p < 0.001). Conclusions: The SUVmax of the primary tumor on florastamin PET/CT was associated with the ISUP-based risk in East Asian men with prostate cancer, suggesting that it could be an imaging biomarker of tumor aggressiveness.