Abstract
OBJECTIVES: To evaluate the relationship between total lesion PSMA (PSMA(TL)), serum PSA, histopathological findings and biochemical recurrence (BCR) in patients with localised prostate cancer (PCa). PATIENTS AND METHODS: This retrospective study assessed men undergoing (68)Ga-PSMA-11 PET/CT for newly diagnosed or treatment-naïve PCa localised to the prostate gland. Volumes of interest were manually mapped to derive SUV(max), SUV(mean), PSMA-avid tumour volume and PSMA(TL). PSMA(TL) was defined as the product of PSMA-avid primary tumour volume and SUV(mean). Spearman correlation tests evaluated associations between PET parameters and PSA, ISUP GG and radical prostatectomy (RP) histopathological outcomes. Associations between PET parameters and clinical outcomes were determined using Cox proportional hazards regression with results presented as HR and 95% CI. RESULTS: A total of 200 patients were included, with a median age of 68 (IQR 62-73) years, PSA of 9.5 (6.6-13.0) ng/ml and follow-up of 41 (25-60) months. Median PSMA(TL) was 29.6 (14.8-54.8) and SUV(max) 11.0 (6.8-17.9). PSMA(TL) and SUV(max) demonstrated a weak correlation with baseline PSA (ρ = 0.334, p < 0.001 and ρ = 0.343, p < 0.001), and PSMA(TL) showed a weak correlation with PSA density in the RP subgroup (ρ = 0.242, p = 0.021). Among 109 (54.5%) patients undergoing RP, PSMA(TL) and SUV(max) showed a weak correlation with ISUP GG (ρ = 0.233, p = 0.015 and ρ = 0.340, p < 0.001). There was a weak correlation between PSMA(TL) and primary tumour stage (ρ = 0.244, p = 0.010) and lymph node stage (ρ = 0.259, p = 0.007). PSMA(TL) was significantly higher in those with seminal vesicle involvement (p = 0.011), perineural invasion (p = 0.025) and lymphovascular invasion (p = 0.002). BCR occurred in 46 patients (42%), with a 1% increased risk of BCR per unit increase in PSMA(TL) (HR 1.01, 95% CI 1.00-1.02, p = 0.011). CONCLUSIONS: PSMA(TL) correlates with PSA, PSA density, ISUP GG, RP histopathological findings and BCR. As an adjunct to SUV(max), PSMA(TL) has the potential to be a useful prognostic tool. Further research is needed to assess its clinical utility.