Biochemical Persistence of Prostate-specific Antigen after Robot-assisted Laparoscopic Radical Prostatectomy: Tumor localizations using PSMA PET/CT imaging

Abstract

Since the introduction of radiolabeled prostate-specific membrane antigen (PSMA) PET/CT, the ability to visualize recurrent prostate cancer has improved substantially. However, diagnostic accuracy is largely lacking for radiolabeled PSMA PET/CT in patients with biochemical persistence (BCP; that is, persistently measurable prostate-specific antigen [PSA] values after robot-assisted laparoscopic radical prostatectomy [RARP]). Therefore, the aim of this study was to determine the role of PSMA (i.e.,¹⁸F-DCFPyL or ⁶⁸Ga-PSMA-11) PET/CT imaging in patients who experience BCP after RARP and to evaluate the sites of persistent disease on PSMA PET/CT. <b>Methods:</b> In total, 150 consecutive patients with BCP after RARP who underwent radiolabeled PSMA PET/CT imaging were retrospectively evaluated. BCP was defined as any detectable first serum PSA value after RARP (≥0.1 ng/mL) at least 6 wk after surgery, in the absence of an undetectable PSA value after RARP. A multivariable logistic regression analysis was performed to identify predictors for the detection of metastases outside the prostatic fossa (≥miN1) on PSMA PET/CT. <b>Results:</b> PSMA PET/CT was performed at a median PSA value of 0.60 ng/mL (interquartile range, 0.3-2.4) after a median of 6 mo (interquartile range, 4-10) after RARP. In total, 101 of 150 patients (67%) had lesions with PSMA expression on PET/CT, and 89 of 150 (59%) had lesions with increased PSMA expression sites outside the prostatic fossa. Moreover, 39 of 150 patients (26%) had PSMA-positive lesions outside the pelvis. On multivariable analysis, higher PSA values after RARP (<i>P</i> = 0.004) and positive pathologic lymph node status (<i>P</i> = 0.006) were independent predictors for ≥miN1. <b>Conclusion:</b> In the presence of BCP, a high proportion of patients already had disease metastatic to the pelvic lymph nodes or showed evidence of distant metastases, as indicated by PSMA PET/CT. Higher PSA levels after RARP and positive pathologic lymph node status were significantly associated with metastases outside the prostatic fossa. In patients with BCP, PSMA PET/CT imaging is warranted to guide salvage treatment strategies.