Prognostic Value of 177Lutetium-PSMA Single Photon Emission Tomography and Timing of Response

Early response assessment is critical for optimizing patient management. Response Evaluation Criteria in Prostate Imaging (RECIP) 1.0, initially developed for Positon Emission Tomography (PET) with 68Ga-PSMA, have demonstrated prognostic value, particularly after two treatment cycles. Recent studies suggest that SPECT at cycle 2 provides prognostic information, although it reflects only the first treatment cycle, whereas PET-based RECIP, assessed after cycle 2, captures the effect of two cycles. This study aims to evaluate the prognostic value of quantitative 177Lu-PSMA-SPECT biomarkers and determine the optimal timing for RECIP-based assessment. It would indeed be very interesting to obtain a prognostic value using imaging performed after treatment, which also provides dosimetry information to organs at risk and to the tumor and/or metastases.