Interreader agreement in evaluation of ⁶⁸Ga-PSMA PET/CT at the time of initial staging: comparison of the three evaluation criteria in the pretreatment risk groups

Abstract

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.