Assessment of Local and Metastatic Recurrence Following Robot-Assisted Radical Prostatectomy by Margin Status Using PSMA PET/CT Scan

<b>Background</b>: Local recurrences following radical prostatectomy (RP) are typically attributed to incomplete surgical resection or positive surgical margins (PSMs). Yet approximately 70% of men with PSMs never experience BCR. Prostate-specific membrane antigen PET scans (PSMA PET) are useful in detecting the incidence and location of recurrence sites. This study explores the relationship between margin status and local and metastatic recurrences using PSMA PET scans. <b>Methods</b>: A retrospective study was conducted with prospectively collected data following RARP with BCR in 159 men undergoing PSMA PET (2017-2023). The primary outcome compared risk and location of recurrences between NSM vs. PSM. A total of 13 cases (8%) had "equivocal" PET scan findings which were assessed first as all positive and then all negative. <b>Results</b>: Of 159 men with BCR undergoing PSMA PET scans, 101 (63.5%) had NSMs and 58 (36.5%) had PSMs. Assuming all 13 "equivocal" scans were positive, the risk of a positive PSMA PET is NSMs vs. PSMs (73% vs. 69% <i>p</i> = 0.56). Local recurrence rates did not differ significantly (NSMs 39.2% vs. PSMs 45% <i>p</i> = 0.55), nor did lymph nodes (NSMs 61% vs. PSMs 58% <i>p</i> = 0.73) or bone lesions (NSMs 16.2% vs. PSMs 22.5% <i>p</i> = 0.41). Multivariate regression analysis showed that margin status was not a predictor of local recurrence (OR 1.40; 95% CI [0.65, 1.54]; <i>p</i> = 0.382). <b>Conclusions</b>: Local recurrence occurs at about the same rate independent of margin positivity status, suggesting that local recurrences appear to be more closely related to metastatic dissemination, not incomplete resection. These findings question the oncologic rationale for wider resections at the expense of functional outcomes.