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Background: Accurate diagnosis and staging are essential for optimal treatment planning of prostate cancer. By combining functional and anatomical imaging, PSMA-PET/mpMRI offers a potential to improve lesion detection and enhance staging accuracy. This study aimed to evaluate the diagnostic performance of lesion detection and local staging of prostate cancer using combined PSMA-PET/mpMRI compared to standalone mpMRI or PSMA-PET.

Results: Fifty-five patients with intermediate- to high-risk prostate cancer scheduled for robot-assisted laparoscopic radical prostatectomy were included. All patients underwent [68Ga]PSMA-PET/mpMRI prior to surgery. Whole-mount histopathology and surgical report served as reference standard. Two radiologists independently evaluated mpMRI, while two nuclear medicine physicians assessed PSMA-PET. For the PSMA-PET/mpMRI analysis, a consensus evaluation was performed by a new set of readers in two teams, each comprising one radiologist and one nuclear medicine physician. Lesion localization was reported based on the PI-RADS v2.1 sector map and compared to histopathology. Among 130 histopathologically confirmed lesions, mean detection rates were 38% (49.5/130) for PSMA-PET/mpMRI, 32% (41/130) for mpMRI and 32% (41/130) for PSMA-PET. For clinically significant prostate cancer (csPC) (≥0.5 ml, ≥ISUP 2; 42 lesions), mean detection rates were 85% (35.5/42) for PSMA-PET/mpMRI, 75% (31.5/42) for mpMRI and 70% (29.5/42) for PSMA-PET. The mean false discovery rates were 8% (PSMA-PET/mpMRI), 15% (mpMRI) and 12% (PSMA-PET). The likelihood of extraprostatic extension (EPE) and seminal vesicle invasion (SVI) were scored using a 5-point Likert scale, where scores of 1–3 were classified as negative and scores of 4–5 were considered positive. Sensitivity for EPE was 32% for PSMA-PET/mpMRI, 37% for mpMRI and 7% for PSMA-PET, with a specificity of 100%, 96% and 98%, respectively. For SVI, sensitivity was 50% for PSMA-PET/mpMRI and 38% for mpMRI and PSMA-PET, with a specificity of 100%, 95% and 97% respectively.

Conclusions: PSMA-PET/mpMRI provided higher and a more consistent performance in localized prostate cancer detection and staging without increasing false-positive findings.