Introduction of semi-automatic whole-body tumor burden assessment in 68Ga-PSMA-11 PET/CT to predict outcome of PSMA-targeted radiologandtherapy

85 Aim: PSMA-targeted radioligand therapy (RLT) is increasingly used in metastastic castration resistant prostate cancer (mCRPC). Whole-body tumor burden is a known to be a prognostic factor in different malignancies. Our aim was to develop a semiautomatic software to assess whole-body tumor burden for mCRPC patients using 68Ga-PSMA-11 PET/CT and to present preliminary data on its application to assess 177Lu-PSMA IT r=-0.52, p=0.12). Discussion: Semiautomatic analyses of PSMA-based tumor volume and total lesion PSMA uptake to describe bone and soft tissue tumor burden in 68Ga-PSMA-11 PET is feasible. PSMA-TV and PSMA-TL are promising quantitative parameters during PSMA-targeted RLT with a high correlation to PSA response. Analysis of larger patient cohorts is necessary to determine its potential prognostic value and to potentially integrate quantitative data to individualise dose concepts.