TY - JOUR T1 - PSMA-ligand uptake in posttherapeutic <sup>177</sup>Lu-PSMA-617 scintigraphy to predict PSA response in patients with advanced mCRPC JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 595 LP - 595 VL - 61 IS - supplement 1 AU - Rudolf Werner AU - Johannes Thiele AU - Tobias Ross AU - Frank Bengel AU - Thorsten Derlin Y1 - 2020/05/01 UR - http://jnm.snmjournals.org/content/61/supplement_1/595.abstract N2 - 595Objectives: Prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) represents a promising treatment option for men afflicted with metastasized castration resistant prostate cancer (mCRPC). However, there is an unmet clinical need for reliable predictors of outcome. We aimed to determine the predictive usefulness of PSMA-ligand uptake on posttherapeutic 177Lu-PSMA-617 scintigraphy, and its relative performance compared to a panel of standard blood-based surrogate markers of disease extent. Methods: A total of 100 consecutive patients with mCRPC were scheduled to receive 2 cycles of 177Lu-PSMA-617 RLT. A panel of baseline conventional laboratory parameters was assessed before initiation of treatment including standard hematology, liver enzymes, alkaline phosphatase and lactate dehydrogenase. Following the first RLT administration, post-therapeutic planar anterior and posterior whole-body-scans were acquired 20-24 h p.i.. Tumor PSMA-ligand uptake was investigated by two independent readers (R) blinded to all clinical information. Based on qualitative visual assessment, PSMA-ligand uptake in metastases was dichotomized into intense PSMA-ligand uptake (i.e. uptake &gt; salivary gland uptake in post therapeutic planar views) and low PSMA-ligand uptake (i.e. uptake ≤ salivary gland uptake in post therapeutic planar views). At 8 weeks after 2 cycles of RLT, percentage (%) PSA decline was assessed, and compared to results of visual assessment of posttherapeutic scans and baseline laboratory values. Results: In 93/100 (93%) patients, PSA was available during follow-up. A median reduction of 47% (IQR, -81.8 to 15.24) in PSA occurred after 2 cycles of RLT, while PSA progression (≥25% increase, PCWG2) was observed in 21/93 (22.6%) of the subjects. R1 rated 58/93 (62.3%) of the scans having intense PSMA-ligand uptake (R2, 60/93 (64.5%); R=0.81, P&lt;0.0001). All investigated conventional laboratory values failed to associate with change in PSA. By contrast, intense PSMA-ligand uptake in PC lesions was significantly associated with %PSA decline (R1, R=0.25; R2, R=0.27; P&lt;0.05). In addition, early PSA progression was associated with low posttherapeutic uptake (R1, R=0.22; R2, R=0.24, P&lt;0.05, respectively), but not with conventional laboratory values. Conclusions: Intense PSMA-ligand uptake of PC metastases (greater than salivary gland uptake) in post-therapeutic scans may hold potential for outcome prediction after PSMA-directed treatment. ER -