Evaluation of Adrenal Metastases in Prostate Cancer Patients with [68GA]GA-PSMA PET/CT Imaging.

Abstract

Objectives: This study aimed to evaluate the imaging and clinical characteristics of adrenal metastases detected by [68Ga]Ga-PSMA PET/CT in prostate cancer patients, with a focus on diagnostic accuracy and prognostic implications. Specifically, we examined the correlation between adrenal lesion characteristics and prognostic markers, such as prostate-specific antigen (PSA) levels and Gleason scores. This study also assessed the diagnostic performance of PSA, standardized uptake value maximum (SUVmax), and Hounsfield Unit (HU) values in differentiating adrenal metastases from benign adrenal adenomas.

Materials and methods: This retrospective study included 44 prostate cancer patients with adrenal lesions identified using [68Ga]Ga-PSMA PET/CT between January 2020 and October 2024. The patients were categorized into two groups: benign adrenal adenomas (n = 16) and adrenal metastases (n = 28). The PET/CT imaging was performed using a 5-ring Discovery IQ PET/CT scanner with QClear reconstruction, following the injection of 2.5 MBq/kg [68Ga]Ga-PSMA ligand and a standardized uptake time of 60 min. The imaging parameters (SUVmax and HU values), clinical characteristics (PSA levels, Gleason scores, and presence of lymphadenopathy), and patient outcomes were analyzed. A ROC analysis was conducted to evaluate the diagnostic performance of these key parameters.

Results: Patients with adrenal metastases had significantly higher PSA levels (mean: 45.6 ± 12.4 ng/mL vs. 18.3 ± 6.7 ng/mL; p < 0.01) and Gleason scores (median: 8 vs. 6; p < 0.01) than those with benign adenomas. SUVmax values were significantly elevated in metastatic lesions (mean: 12.8 ± 4.3 vs. 3.4 ± 1.2; p < 0.001), and HU values were also higher (mean: 45 ± 15 vs. 18 ± 10; p < 0.01). The ROC analysis revealed that SUVmax had the highest diagnostic accuracy (AUC: 0.87), followed by PSA (AUC: 0.85) and HU (AUC: 0.80). Disease progression was observed in 67.9% of metastatic cases versus 18.8% in the adenoma group (p < 0.001), and median overall survival was shorter in metastatic cases (24 months vs. 38 months; p < 0.01).

Conclusions: [68Ga]Ga-PSMA PET/CT is a valuable imaging modality for distinguishing adrenal metastases from benign adenomas in prostate cancer patients. The integration of PSA, SUVmax, and HU values into diagnostic workflows enhances diagnostic precision and improves clinical decision-making. Future research should focus on the prospective validation of these findings in larger cohorts and explore artificial intelligence-based approaches for automated lesion characterization.