Assessing Ga-68 PSMA PET/CT Parameters in Relation to Clinical and Pathological Risk Stratification in Localized Prostate Cancer
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Background Accurate pre-operative risk stratification in prostate cancer is essential, yet conventional imaging poorly reflects tumour burden or aggressiveness. Gallium-68 Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography (Ga-68 PSMA PET/CT) provides combined diagnostic and prognostic insights. This study evaluated PSMA PET metrics for their added value beyond established clinical models. Methods We retrospectively analysed 62 men with localised prostate cancer who underwent Ga-68 PSMA PET/CT before radical prostatectomy. Semi-quantitative indices—SUVmax, SUVmean, SUVpeak, PSMA tumour volume (PSMA-TV), total lesion PSMA uptake (TL-PSMA), and PSMA total-lesion quotient (PSMA-TLQ)—were derived from intraprostatic lesions. These were correlated with pre-operative PSA and four risk systems: D’Amico, ISUP Grade, CAPRA, and the Briganti nomogram. Results PSA correlated significantly with all Ga-68 PSMA PET/CT indices (p < 0.05). Volumetric parameters (PSMA-TV and TL-PSMA) were the most consistent discriminators. TL-PSMA and PSMA-TV showed superior ability to differentiate high- from intermediate-risk disease (AUCs: 0.78 and 0.75) compared to SUV-based metrics (AUCs: 0.68–0.72). For distinguishing D’Amico high-risk from low-risk cancer, TL-PSMA and PSMA-TV achieved excellent performance (AUCs: 0.94 and 0.93). Using the Briganti ≥ 7% threshold, both metrics showed identical AUCs (0.87). Optimal cut-offs were TL-PSMA ≥ 34.6 and PSMA-TV ≥ 2.9, yielding sensitivities of 66–81% and specificities of 84–89%. The visual miPSMA score increased stepwise with ISUP grade and correlated positively with PSA (p = 0.03). Conclusions TL-PSMA and PSMA-TV serve as robust, non-invasive markers of tumour aggressiveness, correlating strongly with multiple clinical risk systems. Ga-68 PSMA PET/CT thus offers prognostic value beyond diagnosis, supporting refined risk stratification and personalised treatment planning.
