Diagnostic performance of 68Ga-PSMA PET/CT in the detection of prostate cancer prior to initial biopsy: comparison with cancer-predicting nomograms

Abstract

Purpose: To assess the diagnostic performance of ⁶⁸Ga-PSMA PET/CT for detecting suspected prostate cancer (PCa) and to compare it with that of two cancer-predicting nomograms.

Methods: We performed a retrospective analysis of 146 consecutive patients with suspected PCa based on symptoms or elevated total prostate-specific antigen (tPSA) levels who underwent ⁶⁸Ga-PSMA PET/CT and histopathologic examinations from April 2017 to April 2018 in a large tertiary care hospital in China. The ⁶⁸Ga-PSMA PET/CT results (PCa or benignancy) were evaluated by two experienced nuclear medicine specialists. The risk of positive PCa was evaluated using ERSPC and PCPT nomograms. The diagnostic performances of ⁶⁸Ga-PSMA PET/CT and that of the two nomograms were compared via receiver operating characteristic (ROC) curve analysis, decision curve analysis, and logistic regression.

Results: A total of 58 patients with tPSA of 0.4-50 ng/ml were included in the final analysis; PCa diagnosis was confirmed in 37 patients and excluded in 21 patients. ROC analysis showed that the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of ⁶⁸Ga-PSMA PET/CT were 91.67, 81.82, 89.19, and 85.71%, respectively, in per-patient analyses. ⁶⁸Ga-PSMA PET/CT exhibited a higher AUC (0.867) than those of ERSPC-RC3 (0.855) and PCPT-RC (0.770). The net benefit of ⁶⁸Ga-PSMA PET/CT was greatest for patients within threshold probabilities of 15-90%. Among the 58 patients, 11 (19%) biopsies suggested by ERSPC-RC3 were unnecessary and could have been avoided if judged by the ⁶⁸Ga-PSMA PET/CT results. Multivariate analysis revealed that the maximum standardised uptake value (SUV_max) and prostate volume were significant predictive factors for positive PCa results.

Conclusion: In suspected PCa patients with tPSA of 0.4-50 ng/ml, ⁶⁸Ga-PSMA PET/CT outperformed the nomograms in predicting cancer and reducing unnecessary biopsies. In addition, the risk of PCa was positively correlated with a higher SUV_max and lower prostate volume, which could help clinicians in making preliminary estimates of individual cancer risk, monitoring ⁶⁸Ga-PSMA PET/CT false-positive results and making biopsy decisions in daily medical practice.

Keywords: 68Ga-PSMA PET/CT; Biopsy; Decision curve analysis; Multivariate analysis; Nomogram; Prostate cancer.