18F-PSMA-1007 PET/CT in Primary Prostate Cancer: Using tPSA to Detect Distant Metastasis and Incorporating SUVmax to Characterize Primary Prostate Cancer and Distant Metastasis

Abstract PurposeTo evaluate the diagnostic performance of total prostate-specific antigen (tPSA) for primary prostate cancer (PCa) distant metastasis in 18F-PSMA-1007 PET/CT, and the potential mediation role of tPSA level on the maximum standardized uptake value (SUVmax) of different metastasis stages.MethodsRetrospective analysis was performed on 101 patients admitted consecutively between March 2019 and June 2020 with biopsy proven PCa who were referred for PET/CT. The diagnostic performance of tPSA to detect distant metastasis was evaluated using receiver operating characteristic curve (ROC) and logistic regression analyses. SUVmax was compared across different metastatic stages with either low or high tPSA level using analysis of variance (ANOVA). A path analysis was conducted to evaluate the mediating effect of tPSA level on the relation between SUVmax of primary PCa and SUVmax of metastatic foci.ResultsAt a value of 29.01, the prediction tPSA demonstrated a sensitivity of 57.14% and a specificity of 73.68% for detecting distant metastasis with an area under the curve of 0.656 (P = 0.004). The prediction tPSA level was the only significant predictive variable in a logistic regression model (P = 0.008, odds ratio = 3.273). SUVmax was significantly different between primary prostate tissue with metastasis and metastasis foci only when tPSA ≥ 29.01 (P = 0.001). In addition, for those with metastasis foci, SUVmax was significantly higher in those with tPSA ≥ 29.01 than those with tPSA < 29.01 (P = 0.034). Both tPSA and SUVmax associated with risk of metastasis (P = 0.008, P = 0.014), and tPSA was found to have a partial mediating effect on SUVmax of primary PCa and metastases foci (P < 0.05). ConclusionA prediction tPSA level of 29.01 can help predict the distant metastases in primary PCa. The incorporation of 18F-PSMA-1007 PET/CT in PCa evaluation may better characterize the metastasis lesions.