Background: PSMA-PET was positive for distant metastases (39% distant nodes, 24% bone, 6% visceral organ) in >50% of nmCRPC pts who were nonmetastatic by conventional imaging (Fendler et al. CCR 2019). However, the prognostic impact of PSMA-PET disease extent and its association with oncologic outcomes is unknown. We assessed the prognostic utility of PSMA-PET disease extent in nmCRPC pts defined by conventional imaging for OS and new metastases-free survival (nMFS). Methods: 200 pts (6 centers) with nmCRPC by conventional imaging and prostate-specific antigen doubling time (PSADT) ≤10 mo and/or ISUP grade group ≥4 underwent PSMA-PET. Clinical course and treatment management after PSMA-PET imaging were recorded for 4-9 y. Pt characteristics and PSMA-PET disease extent were analyzed retrospectively. OS and PSMA-PET nMFS (time from primary PSMA-PET to appearance of new distant metastases by PSMA-PET or death) were analyzed for pt subgroups based on disease extent by univariate Cox regression. Results: Median OS was 74 mo, similar to the SPARTAN study of nmCRPC pts (74 mo; Smith et al. Eur Urol 2021). Polymetastatic disease (≥5 distant lesions by PSMA-PET) was associated with shorter OS (median 61 mo vs not reached [NR]) and shorter PSMA-PET nMFS (HR 1.8, 95% CI 1.1-2.9; median 38 vs 60 mo; p=0.021). Any metastatic disease by PSMA-PET and whole-body PSMA tumor volume were not prognostic for OS and PSMA-PET nMFS (all p>0.05). Initial pN1 status was associated with shorter OS (median 55 mo vs NR), but not with PSMA-PET nMFS (p>0.05). Baseline age, baseline Gleason grade ≥8, prior radiotherapy (RT), and PSA and PSADT at time of primary PSMA-PET were not associated with outcomes (all p>0.05). Management after PSMA-PET imaging was mostly local/targeted therapy in pts with no visible/locoregional disease (40/30%) and androgen receptor signaling inhibition therapy in pts with nodal/bone distant metastases (35/43%). Conclusions: Polymetastases (>5) by PSMA-PET and initial pN1 status were significantly associated with worse OS. PSMA-PET disease extent provides a potential novel additional risk stratification for pts with nmCRPC without distant metastasis based on conventional imaging. Further validation is needed to prove its independent prognostic value. Clinical trial information: NCT01946204.

^an=132, *p<0.05.