M. Bieth, M. Krönke, R. Tauber, M. Dahlbender, M. Retz, S. Nekolla, B. Menze, T. Maurer, M. Eiber, M. Schwaiger Exploring New Multimodal Quantitative Imaging Indices for the Assessment of Osseous Tumour Burden in Prostate Cancer using 68Ga-PSMA-PET/CT Journal of Nuclear Medicine (bib)
	Positron-emission-tomography (PET) combined with computed-tomography (CT) and prostate-specific-membrane-antigen (PSMA) ligands has gained significant interest for staging prostate cancer (PC). In this study, we propose two multimodal quantitative indices as imaging biomarker for the assessment of osseous tumour burden using 68Ga-PSMA-PET/CT and present preliminary clinical data. We define two Bone-PET-Indices (BPI) that incorporate anatomical information from CT and functional information from 68Ga-PSMA-PET: BPIVOL is the percental bone volume affected by tumour. BPISUV additionally considers the level of PSMA-expression. We describe a semi-automatic computation method based on segmentation of bones in CT and of lesions in PET. Data from 45 patients with castration-resistant PC and bone metastases during Radium-223-dichloride were retrospectively analysed. We evaluated the computational stability and reproducibility of the proposed indices, and explored their relation to the prostate-specific-antigen (PSA) blood value, the Bone-Scan-Index (BSI) and disease classification using the PET response criteria in solid tumours (PERCIST). On the technical side, BPIVOL and BPISUV showed an inter-observer maximum difference of 3.5% and their computation took only a few minutes. On the clinical side, BPIVOL and BPISUV showed significant correlations with BSI (r=0.76 and 0.74 respectively, p<0.001) and PSA-values (r=0.57 and 0.54 respectively, p<0.01). When comparing the proposed indices against expert rating using PERCIST, BPIVOL and BPISUV showed better agreement than BSI, indicating their potential for objective response evaluation. We propose the evaluation of BPIVOL and BPISUV as imaging biomarkers for 68Ga-PSMA-PET/CT in a prospective study exploring their potential for outcome prediction in patients with bone metastases from PC.</TD>
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