Development of standardized image interpretation for 68Ga-PSMA PET/CT to detect prostate cancer recurrent lesions
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After primary treatment, biochemical relapse (BCR) occurs in a substantial number of patients with prostate cancer (PCa). PET/CT imaging with prostate-specific membrane antigen based tracers (68Ga-PSMA) has shown promising results for BCR patients. However, a standardized image interpretation methodology has yet to be properly agreed. The aim of this study, which was promoted and funded by European Association of Nuclear Medicine (EANM), is to define standardized image interpretation criteria for 68Ga-PSMA PET/CT to detect recurrent PCa lesions in patients treated with primary curative intent therapy (radical prostatectomy or radiotherapy) who presented a biochemical recurrence. In the first phase inter-rater agreement between seven readers from seven international centers was calculated on the reading of 68Ga-PSMA PET/CT images of 49 patients with BCR. Each reader evaluated findings in five different sites of recurrence (local, loco-regional lymph nodes, distant lymph nodes, bone, and other). In the second phase the re-analysis was limited to cases with poor, slight, fair, or moderate agreement [Krippendorff’s (K) alpha<0.61]. Finally, on the basis of the consensus readings, we sought to define a list of revised consensus criteria for 68Ga-PSMA PET/CT interpretation.
Between-reader agreement for the presence of anomalous findings in any of the five sites was only moderate (K’s alpha: 0.47). The agreement improved and became substantial when readers had to judge whether the anomalous findings were suggestive for a pathologic, uncertain, or non-pathologic image (K’s alpha: 0.64). K’s alpha calculations for each of the five sites of recurrence were also performed and evaluated. First Delphi round was thus conducted. A more detailed definition of the criteria was proposed by the project coordinator, which was then discussed and finally agreed by the seven readers. After the second Delphi round only four cases of disagreement still remained. These were evaluated for a final round, allowing a final agreement table to be written.
We hope that by developing these consensus guidelines on the interpretation of 68Ga-PSMA PET/CT, clinicians reporting these studies will be able to provide more consistent clinical reports and that within clinical trials, abnormality classifications will be harmonized, allowing more robust assessment of its diagnostic performance.
KeywordsPSMA Pet/Ct Prostate cancer Biochemical recurrence Consensus guidelines Criteria
The authors would like to acknowledge the EANM team for its support and help throughout the study design and preliminary work fundamental to the outcome of the study, Sonja Niederkofler and Henrik Silber for their logistical and administrative support.
Also, for his technical support, the authors would like to acknowledge Jason Callahan from Peter MacCallum cancer centre (Melbourne, AUS).
Compliance with ethical standards
The project was promoted and funded by European Association of Nuclear Medicine (EANM).
Conflict of interest
Author SF is Advisory board of BED, Bayer, ANMI and received travel support from Bayer, GE Healthcare, Sanofi.
Author ME received a Research grant from Siemens Medical Solutions.
Author SC is co-founder of University of Torino spin-off Dixit srl, that distributes Widen system used in this investigation.
Author MS received a research grant from Siemens Medical Solution.
Author BJK received Research Grants from Bayer, Schering/Pharma, TauRx, Therapeutics, Piramal, AMGEN and Travel Grants & honoraria from Jannsen-Cilag, Astellas.
All other authors have no conflict of interest to declare.
Ethical approval and informed consent
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.
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