For patients undergoing primary staging of prostate cancer, multiparametric magnetic resonance imaging (mpMRI) and 68Ga-prostate specific membrane antigen (PSMA)-positron emission tomography (PET)/MRI have similar interreader agreement for extraprostatic extension (≥T3), while 68Ga-PSMA-PET/MRI has higher agreement for regional lymph node metastasis (N1), according to a study published online in the European Journal of Radiology.
Stephan M. Skawran, MD, from University Hospital Zurich, and colleagues compared mpMRI and 68Ga-PSMA-PET/MRI for primary staging of prostate cancer among 49 patients who underwent both tests during January 2016 to February 2019. ≥T3 and N1 were rated by two readers each on mpMRI and 68Ga-PSMA-PET/MRI.
The researchers found that interobserver agreement for ≥T3 was κ = 0.58/0.47 and N1 was κ = 0.55/0.92 for mpMRI and 68Ga-PSMA-PET/MRI, respectively. For mpMRI readers 1 and 2 versus 68Ga-PSMA-PET/MRI readers 3 and 4, diagnostic accuracy measured with the area under the receiver operating characteristic curve (AUC) was 0.72 and 0.62 versus 0.71 and 0.72 for ≥T3 and 0.39 and 0.55 versus 0.72 and 0.78 for N1. Diagnostic accuracies delivered by quantitative parameters were 0.70 to 0.72 for ≥T3. For N1, the 2018 Briganti model achieved an AUC of 0.89.
“Due to the high costs and sparse availability, identifying patients who will benefit from primary staging using 68Ga-PSMA-PET imaging is of utter importance,” the authors wrote. “68Ga-PSMA-PET/MRI demonstrated comparable diagnostic accuracy for staging of extracapsular extension and higher interobserver-agreement and diagnostic accuracy for regional lymph node metastasis than mpMRI.”
One author disclosed receiving grants from GE Healthcare.