Background/objectives:Accurate and uniform interpretation and reporting of metastatic prostate
cancer (PCa) lesions on prostate-specific membrane antigen (PSMA) positron
emission tomography/computed tomography (PET/CT) are indispensable.18F-PSMA-1007 is increasingly used because of its favorable
imaging characteristics. However, increased non-specific skeletal uptake may
be an important pitfall of this radioligand. Therefore, we aimed to assess
the interobserver variation in reporting skeletal18F-PSMA-1007
uptake on PET/CT.Design/methods:In total, 3318F-PSMA-1007 PET/CT scans of 21 patients with
primary PCa and 12 patients with biochemical recurrence were included, and a
total of 85 skeletal lesions were evaluated by three independent observers.
The primary endpoint was the interobserver variability of the likelihood of
malignancy of the skeletal lesions on both patient and lesion level (kappa
analysis).Results:Observers qualified most lesions as not malignant (81–91%) and the overall
mean interobserver agreement was moderate on both patient (κ: 0.54) and
lesion level (κ: 0.55). In 52 lesions without corresponding CT substrate,
the rating resulted in not malignant in 95–100%. Availability of additional
imaging (60% of lesions) did not improve interobserver agreement (κ: 0.39 on
lesion level) and resulted in unchanged rating for all observers in 78%.Conclusion:This interobserver analysis of skeletal18F-PSMA-1007 uptake
resulted in moderate agreement, in line with rates reported in literature.
Importantly, the presence of non-specific skeletal uptake without CT
substrate, as a potential shortcoming of18F-PSMA-1007, did not
impair interobserver agreement.