Purpose To assess 68Ga-PSMA PET/CT for detection of low- and intermediate-risk prostate cancer (PCa), high-risk PCa in comparison with mpMRI, respectively, and to determine which of low- and intermediate-risk PCa are more likely to be detected by 68Ga-PSMA PET/CT. Methods We conducted a retrospective analysis of patients who had undergone a prostate biopsy and/or radical prostatectomy and who were scanned with 68Ga-PSMA PET/CT and mpMRI between June 2019 and March 2021. The mpMRI images were scored with the Prostate Imaging-Reporting and Data System Version 2.1 (PI-RADS) and were classified as either negative (PI-RADS 1–3) or positive (PI-RADS 4–5). Suspicious 68Ga-PSMA PET/CT lesions were reviewed for each relevant patient and classified by double-trained board-certified nuclear medicine physicians. The results were evaluated with the histopathological outcome. All patients were classified according to the D’Amico classification, and the clinical data were combined for stratified analysis. Result A total of 101 patients who were pathologically diagnosed with PCa were analyzed. Of the 101 patients, 88 (80.6%) patients presented with a pathologic mpMRI, and 85 (79.1%) with a pathologic 68Ga-PSMA PET/CT. In the high-risk PCa cohort, 68Ga-PSMA PET/CT was positive in 64/66 (97.0%) patients and yielded a higher detection rate than that for the mpMRI patients (58/66, 87.9%; p < 0.05). However, mpMRI provided superior diagnostic confidence in identifying low- and intermediate-risk PCa (30/35, 85.7% vs. 21/35, 60.0%; p < 0.05). When the age threshold exceeded 62.5 years and the serum prostate specific antigen (PSA) threshold exceeded 9.4 ng/ml, a higher uptake of PSMA was more likely to occur in the lesions of low- and intermediate-risk PCa. Conclusion The diagnostic performance of 68Ga-PSMA PET/CT was superior to that of mpMRI in the high-risk PCa cohort, which was consistent with prior studies. Furthermore, in the initial diagnosis of low- and intermediate-risk PCa, we found that mpMRI showed a higher diagnostic accuracy than 68Ga-PSMA PET/CT did. Low- and intermediate-risk PCa patients with a PSA ≥ 9.4 ng/ml and age ≥ 62.5 years were more likely to have a positive 68Ga-PSMA PET/CT result.

Background: Prostate imaging reporting and data system (PI-RADS) category 3 lesions represent a "gray zone," having an equivocal risk of presenting as clinically significant prostate cancer (csPCa). 68 Ga-labelled prostate-specific membrane antigen ( 68 Ga-PSMA) positron emission tomography/computed tomography (PET/ CT) has been identified as a diagnostic tool that can help to predict cases of primary PCa. We aimed to explore diagnostic value of 68 Ga-PSMA PET/CT for csPCa in PI-RADS 3 lesions to aid in decision-making and avoid unnecessary biopsies.Methods: A total of 78 men with PI-RADS 3 lesions who underwent both 68 Ga-PSMA PET/CT and transrectal ultrasound/magnetic resonance imaging (MRI) fusion-guided biopsy were enrolled. Images were analyzed by respective physicians who were blinded to the pathological results. Receiver operating characteristic (ROC) curve analysis and decision curve analysis were used to evaluate the diagnostic performance of univariate and multivariate analyses.Results: A total of 26/78 men had pathologically confirmed csPCa. A lower ADCT/ ADCCLP (0.65 vs. 0.71, p = 0.018), smaller prostate volume (25.27 vs. 42.79 ml, p < 0.001), lower free prostate-specific antigen/total prostate-specific antigen (0.11 vs. 0.16, p < 0.001), higher PSA level (13.45 vs. 7.90 ng/ml, p = 0.001), higher PSA density (0.40 vs. 0.16 ng/ml 2 , p < 0.001), higher SUVmax (9.80 vs. 4.40, p < 0.001) and SUVT/BGp (2.41 vs. 1.00, p < 0.001) were associated with csPCa. ROC analysis illustrated the improvement in SUVmax and SUVT/BGp compared with all independent and combined clinical features as well as multiparametric magnetic resonance imaging (mpMRI) features for csPCa detection. The net benefits of SUVmax and SUVT/BGp were superior to those of other features, respectively. With cutoff values of 5.0 for SUVmax and 1.4 for SUVT/BGp, the diagnostic sensitivity and specificity for csPCa were 96.2%, 100% and 80.8%, 84.6%, respectively. Conclusion:68 Ga-PSMA PET/CT is potentially capable of stratifying men with PI-RADS 3 lesions according to the presence of csPCa and has better performance than the model established based on clinical and mpMRI features.

Malignant peritoneal mesothelioma is a rare malignancy that may manifest as extraperitoneal metastasis. We describe the findings of 68 Ga-FAPI and 18 F-FDG PET/CT in a case of malignant peritoneal mesothelioma with widespread muscle metastasis in a butterfly-shaped distribution pattern. We found that FDG and FAPI uptake in the peritoneal tumor and its spread were inhomogeneous. Notably, 68 Ga-FAPI PET/CT more clearly showed relevant lesions compared with 18 F-FDG PET/CT.

Background: Xanthogranulomatous prostatitis (XGP) is a rare disorder of the prostate. It presents as a hard fixed nodule on digital rectal examination (DRE), and may cause obstructive urinary symptoms and elevated serum prostate-specific antigen (PSA) levels, therefore mimicking prostate cancer (PCa) clinically and biochemically. Radiological features of XGP overlap with those of PCa, and the 2 conditions cannot be distinguished by pelvic multiparametric magnetic resonance imaging (mpMRI). 68 Ga-labelled prostatespecific membrane antigen ( 68 Ga-PSMA) with positron emission tomography/computed tomography (PET/ CT) has shown its potential in the initial diagnosis and staging of PCa; however, the imaging characteristics of XGP on 68 Ga-PSMA PET/CT have yet to be reported.Case Description: We report the case of a 56-year-old man who had slowly progressing dysuria for 10 years, which was significantly worse for 1 week, and a PSA level of 49.19 ng/L. Ultrasound revealed a hypoechoic lesion in the left periphery of the prostate, which was hypointense with capsular irregularity on axial T2-weighted imaging (T2WI), hyperintense on the diffusion weighted imaging (DWI), and hypointense on the apparent diffusion coefficient (ADC) maps resulting in a Prostate Imaging-Reporting and Data System (PI-RADS) score of 5. The patient was highly suspected of having high-risk PCa and underwent a 68 Ga-PSMA PET/CT for staging. The PET/CT images showed no PSMA uptake in the involved region. Considering that a small proportion of cases of PCa do not express PSMA, a subsequent targeted biopsy was performed, guided by mpMRI. Histopathological examination showed a large number of foamy macrophages in the neutrophile granulocyte infiltrate, and XGP was finally diagnosed. After treatment with antibiotic levofloxacin, the patient's PSA returned to normal, and his dysuria symptoms had disappeared at the 2-month follow-up.Conclusions: Non-uptake of PSMA in a lesion may still provide information for a diagnosis by exclusion or regular follow-up checks in patients that are highly suspected to have PCa in clinic or on mpMRI.