RT Journal Article SR Electronic T1 High concordance rate on SSTR-RADS version 1.0 as a reporting system for SSTR PET imaging and selection of potential PRRT candidates JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 363 OP 363 VO 61 IS supplement 1 A1 Werner, Rudolf A1 Derlin, Thorsten A1 Rowe, Steven A1 Bundschuh, Lena A1 Sheikh, Gabriel A1 Pomper, Martin A1 Buck, Andreas A1 Bengel, Frank A1 Bundschuh, Ralph A1 Lapa, Constantin YR 2020 UL http://jnm.snmjournals.org/content/61/supplement_1/363.abstract AB 363Objectives: Recently, a standardized framework system for interpreting somatostatin receptor (SSTR)-targeted PET/CTs, termed SSTR-Reporting and Data System (RADS) 1.0, has been introduced providing reliable standards and criteria for SSTR PET. We determined the interobserver reliability of SSTR-RADS for interpretation of 68Ga-DOTATOC PET/CT scans in a multicentric, randomized setting. Methods: A set of 51 randomized 68Ga-DOTATOC PET/CT scans was independently assessed by four blinded readers with different levels of experience (2 experienced readers (ER) and 2 inexperienced readers (IR)) trained with SSTR-RADS 1.0 criteria (based on a 5-point scale (from 1 = definitively benign to 5 = high certainty that neuroendocrine tumor is present)). Per scan, SSTR-RADS scores were assigned to a maximum of 5 target lesions (TL). An overall scan impression based on SSTR-RADS was indicated, and interobserver agreement rates on a TL-based, on an organ-based, and on an overall SSTR-RADS score-based level were computed. Readers were also asked to indicate whether peptide receptor radionuclide therapy (PRRT) should be considered based on the assigned RADS scores. Results: Among the selected TL, 153 were chosen by at least 2 individual observers (all 4 readers selected the same target lesion in 58 of 153 [37.9%] instances). The interobserver agreement for SSTR-RADS scoring among identical TL was good (intraclass correlation coefficient [ICC] for 4, 3, and 2 identical target lesions, ≥0.73, respectively). For lymph node and liver lesions, excellent interobserver agreement rates were derived (ICC, 0.91 and 0.77, respectively). Moreover, the interobserver agreement for an overall scan impression based on SSTR-RADS was excellent (ICC, 0.88). Decision for PRRT based on SSTR-RADS demonstrated an excellent agreement with an ICC of 0.8. No significant differences between ER and IR for overall scan impression and TL-based analyses were observed (p≥0.18, respectively), thereby suggesting that SSTR-RADS seems to be readily applicable even for less experienced readers. Conclusions: SSTR-RADS criteria demonstrated a high concordance rate, even among readers with different experience, supporting the adoption of SSTR-RADS for trials, or clinical routine. Further increase in interobserver reliability could be derived by stricter advice on selecting TL.