Articles

The accuracy of PSMA PET/CT for assessing intraprostatic lesions in patients with prostate cancer: An evaluation of the PI-RADS, PRIMARY and PSMA-expression score

BJMO - volume 19, issue 2, march 2025

E. Donck MD, P. de Visschere MD, PhD, C. Van Praet MD, PhD, S. Verbeke MD, PhD, S. Hendrickx MD, C. Berquin MD, S. Rottey MD, PhD, W. Verla MD, PhD, N. Lumen MD, PhD

SUMMARY

Background: Magnetic Resonance Imaging (MRI) is advised for the diagnosis of prostate cancer (PC), and PSMA PET/CT is used for distant staging of PC. Local staging of the primary tumour with PSMA PET/CT is currently not recommended, although the primary lesion can be visualised as well. Recently, two new tumour-assessing scores were developed to optimise the diagnostic accuracy of PSMA PET/CT for the primary tumour: the PSMA-expression score and the PRIMARY score.

Objective: To evaluate the performance of PSMA PET/CT and its PRIMARY and PSMA-expression scores in the assessment of intraprostatic lesions in patients with PC. Patients and methods: This is a retrospective analysis of patients treated with radical prostatectomy for PC in a single tertiary centre between 2019 and 2022. All patients underwent preoperative prostate MRI and 18F- or 68Ga-PSMA-11 PET/CT. The medical images were pseudonymized and retrospectively assessed by two radiologists and a nuclear medicine specialist. The PSMA PET/CTs were scored according to the PSMA-expression score (PROMISE V2 framework) and the PRIMARY score. The MRIs were scored using the PI-RADS system. The accuracy of the three different scores for diagnosing high-grade PC (ISUP grade ≥3) was evaluated.

Results: The PSMA-expression score demonstrated the highest accuracy for detecting high-grade PC, with an AUC of 0.76, outperforming the PI-RADS scores from reader 1 (AUC of 0.59) and reader 2 (AUC of 0.68) and the PRIMARY score (AUC of 0.69). It had a sensitivity of 72%, a specificity of 70%, a positive predictive value of 85%, and a negative predictive value of 51%.

Conclusion: PSMA PET/CT has a promising diagnostic accuracy to detect intraprostatic lesions of high grade in patients with PC. Further validation of the PSMA PET scoring systems is warranted.

Patient summary: In this study, the performance of PSMA PET/CT (the PRIMARY and PSMA-expression scores) to detect malignant lesions in the prostate was evaluated. PSMA PET/CT and these scoring systems seem promising to detect PC and could be of interest in cases where MRI is ambiguous.

(BELG J MED ONCOL 2025;19(2):46–53)

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