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Objective: The aim of this study was to assess the interreader agreement in evaluation 68Ga-prostate-specific membrane antigen (PSMA) PET/CT according to three current criteria European association of nuclear medicine, PROMISE with miTNM, and PSMA-RADS in newly diagnosed prostate cancer (PC) patients., Methods: The images of 101 patients who had been diagnosed with PC and underwent 68Ga-PSMA PET/CT at the time of initial staging were evaluated according to the three interpretation criteria by two nuclear medicine specialists. Local tumor, pelvic lymph node metastasis and distant metastasis were evaluated separately. Abdominal lymph nodes, bone and visceral organ metastases were additionally evaluated as subregions of distant metastatic sites. Patients were evaluated in subgroups Gleason score ≥8 or prostate-specific antigen ≥20 ng/mL as the high-risk group (HR) and prostate-specific antigen ≤ 20 ng/mL and Gleason score <8 as the low-risk group (LR). To measure interreader agreement for each judgment site Cohen's Kappa statistic coefficient (κ) was calculated., Results: All three criteria European association of nuclear medicine, PROMISE with miTNM and PSMA-RADS exhibit substantial and almost perfect agreement between the readers in all sites except for PSMA-RADS in bone and visceral metastasis (κ = 0.495, κ = 0.506, respectively). According to the risk groups, a remarkable difference in interreader agreement for bone metastasis for all three criteria (especially in PSMA-RADS) between the HR and LR patients was detected., Conclusions: In low-risk patients especially PSMA-RADS criteria leads to increased interreader reporting differences. While evaluating 68Ga-PSMA PET/CT images it should be considered that pretreatment risk levels of PC patients could affect the interreader agreement., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Aim: In this study, we aimed to measure interobserver and intraobserver agreement in Ga-68-prostate-specific membrane antigen (PSMA) PET/computed tomography (CT) image interpretation. In addition, the limitations of these criteria and levels of personal confidence reported by the readers when reporting the findings were determined. The effects of interpersonal differences on clinical decisions were also investigated., Methods: PSMA PET images from 133 cases were reported independently by four different readers at different times according to the molecular imaging TNM (miTNM) and PSMA-reporting and data system (RADS) templates., Results: There was substantial interobserver agreement for overall positivity, miT, miN and miM staging (Fleiss' κ = 0.65, 0.625, 0.731, and 0.779). Substantial agreement levels were observed in reporting of seminal vesicle invasion, the number of lymph node stations with metastasis, total number of intraprostatic areas containing tumors, and lymph node metastasis staging (Fleiss' κ = 0.622 and 0.779). The highest variation was seen in the reporting of intraprostatic distribution: In International Society of Urological Pathology (ISUP) grade group 1, moderate agreement was observed, and it was seen that the agreement level for the T staging increased with an increasing ISUP group in the staging group (Fleiss' κ = 0.531 vs. 0.655). There was near-perfect interobserver agreement in the reporting of five-point PSMA-RADS scoring [intraclass correlation coefficient (ICC) κ = 0.904; 95% CI, 0.865-0.934]. Disagreement according to miTNM staging had a major effect on clinical management in only 9% (n = 12) of the patients., Conclusion: PSMA PET has a lower interobserver variability and higher reproducibility than other imaging methods used for imaging of prostate cancer do, including CT, MRI, and bone scintigraphy. The miTNM template provides a reporting format that is highly reproducible and has a high level of agreement among readers, but the prostatic template needs development. In contrast, the PSMA-RADS system leads to slightly increased interobserver reporting differences and reduces personal confidence, but at the same time, it still exhibits almost-perfect agreement in terms of scoring.