Abstract
1563
Objectives: To compare three interpretation criteria of 68Ga-PSMA PET (EANM, PROMISE, and PSMA-RADS) by evaluating inter- and intra-reader agreement.
Methods: 78 patients were enrolled in this retrospective study. Our cohort consisted of two groups as follows: group 1 including 40 patients (mean age, 70.3±7.0 years old) who underwent 68Ga-PSMA PET/CT due to biochemical recurrence of prostate cancer, and group 2 including 38 patients (mean age, 64.9±5.9 years old) who underwent 68Ga-PSMA PET/MRI for initial staging of biopsy-proven prostate cancer. Two nuclear medicine physicians independently evaluated all 68Ga-PSMA PET/CT and PET/MRI studies according to the three interpretation criteria. They reevaluated all studies 6 months later in the same manner and blinded to the initial reading. K’s alpha was calculated to evaluate inter- and intra-reader agreement in each criterion based on the following sites: prostate bed after radical prostatectomy or primary tumor, lymph node metastasis, and distant metastasis. The second reading was used to calculate inter-reader agreement. The degree of agreement according to K’s alpha was considered as follows: 0.00-0.20 = slight agreement, 0.21-0.40 = fair agreement, 0.41-0.60 = moderate agreement, 0.61-0.80 = substantial agreement, 0.81-1.00 = almost perfect agreement.
Results: In group 1, inter-reader agreement reached moderate to almost perfect except judgement of distant metastasis based on PSMA-RADS (K’s alpha = 0.22), in which the most frequent cause of disagreement were small lung nodules. In group 2, judgement of primary tumor showed fair inter-reader agreement in all of the three criteria. Judgement of distant metastasis based on PSMA-RADS showed slight agreement (K’s alpha = 0.12) due to findings pointed out only by one reader as possible other malignancies. Intra-reader agreement reached moderate to almost perfect except judgement of distant metastasis based on EANM by one reader (K’s alpha = 0.38).
Conclusions: Three published criteria have good reproducibility in evaluating 68Ga-PSMA PET by each reader, but there are some factors bringing inter-reader disagreement. This indicates that further works are needed to address the issue.