The Association Between [⁶⁸Ga]PSMA PET/CT Response and Biochemical Progression in Patients with High-Risk Prostate Cancer Receiving Neoadjuvant Therapy

Abstract

Our previous study found that the prostate-specific membrane antigen (PSMA) PET/CT response of primary prostate cancer (PCa) to neoadjuvant therapy can predict the pathologic response. This study was designed to investigate the association between [⁶⁸Ga]PSMA PET/CT changes and biochemical progression-free survival (bPFS) in high-risk patients who underwent neoadjuvant therapy before radical prostatectomy (RP). <b>Methods:</b> Seventy-five patients with high-risk PCa in 2 phase II clinical trials who received neoadjuvant therapy before RP were included. The patients received androgen deprivation therapy plus docetaxel (<i>n</i> = 33) or androgen deprivation therapy plus abiraterone (<i>n</i> = 42) as neoadjuvant treatment. All patients had serial [⁶⁸Ga]PSMA PET/CT scans before and after neoadjuvant therapy. Age, initial prostate-specific antigen level, nadir prostate-specific antigen level before RP, tumor grade at biopsy, treatment regimen, clinical T stage, PET imaging features, pathologic N stage, and pathologic response on final pathology were included for univariate and multivariate Cox regression analyses to identify independent predictors of bPFS. <b>Results:</b> With a median follow-up of 30 mo, 18 patients (24%) experienced biochemical progression. Multivariate Cox regression analyses revealed that only SUV_max derived from posttreatment [⁶⁸Ga]PSMA PET/CT and pathologic response on final pathology were independent factors for the prediction of bPFS, with hazard ratios of 1.02 (95% CI, 1.00-1.04; <i>P</i> = 0.02) and 0.12 (95% CI, 0.02-0.98; <i>P</i> = 0.048), respectively. Kaplan-Meier analysis revealed that patients with a favorable [⁶⁸Ga]PSMA PET/CT response (posttreatment SUV_max < 8.5) or a favorable pathologic response (pathologic complete response or minimal residual disease) had a significantly lower rate of 3-y biochemical progression. <b>Conclusion:</b> Our results indicated that [⁶⁸Ga]PSMA PET/CT response was an independent risk factor for the prediction of bPFS in patients with high-risk PCa receiving neoadjuvant therapy and RP, suggesting [⁶⁸Ga]PSMA PET/CT to be an ideal tool to monitor response to neoadjuvant therapy.