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AI-derived PSMA-positive tumor volume calculations demonstrate repeatability consistent with RECIP 1.0 criteria when the same radiotracer is used, but inter-tracer assessments yield substantially wider repeatability limits, necessitating the use of consistent radiotracers for response evaluation. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.SUPPORTS_CONSENSUS.

October 30, 2025La radiologia medica1 citationsOpen Access

Deep learning-based PSMA PET segmentation repeatability: A post-hoc analysis of a single-center, prospective, test–retest trial

JKJake KendrickThe University of Western Australia RFRoslyn J. FrancisThe University of Queensland GHGhulam Mubashar HassanThe University of Western Australia

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Abstract

The primary aim of this study was to quantify the subject-level test–retest repeatability of artificial intelligence (AI)-derived PSMA PET imaging biomarkers using a previously developed model. The secondary aim was to assess the performance of this segmentation model, which was trained on 68 GaGa-PSMA-11 PET scans, on 18FF-PSMA-1007 PET scans. This was a post-hoc analysis of a prospective, single-center, test–retest trial. Seventeen patients with metastatic prostate cancer (mPCa) were randomised into groups, either receiving the same tracer (68 GaGa-PSMA-11 or 18FF-PSMA-1007) for both scans (intra-tracer group, n = 9) or a different tracer (inter-tracer group, n = 8). Scans were delineated using a fully automated AI method and semi-automatically. The subject-level repeatability of four imaging biomarkers, including PSMA-positive tumour volume, was quantified. Repeatability analysis demonstrated poorer repeatability for all biomarkers in the inter-tracer group. In the intra-tracer group, the AI-derived PSMA-positive tumour volume had a repeatability coefficient of 13.8% for higher volume disease patients (≥ median tumour volume). There was no significant difference in the per-scan lesion-level positive predictive value of the AI model between 68 GaGa-PSMA-11 and 18FF-PSMA-1007 PET scans (0.88, IQR 0.69—1.00 vs. 0.78, IQR 0.54—1.00, p = 0.60). AI-based PSMA-positive tumour volume calculations have repeatability limits that are consistent with the use of the Response Evaluation Criteria in PSMA PET/CT (RECIP 1.0) criteria for higher volume disease patients when the same tracer is used. Substantially wider repeatability limits in the inter-tracer group provide evidence that response assessment should be conducted using the same radiotracer.

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