Role of non-contrast CT component of prostate-specific membrane antigen PET/CT scan in the detection of peripheral zone prostate cancer

Objective: The aim of this study was to look for feasibility of non-contrast CT (NCCT) in detecting peripheral zone prostate cancer (PCa). Methods: A retrospective analysis included 50 biopsy-proven PCa patients between April 2019 and March 2022 who underwent staging whole body prostate-specific membrane antigen (PSMA)/CT prior to treatment. The control subjects were 50 randomly selected adult male patients who underwent PET/CT for non-prostate malignancy during the same time period. Two readers independently calculated the Hounsfield unit (HU) of normal peripheral zone, central zone, and corresponding PSMA avid focus in cases. Results: No significant difference was seen in the mean HU value of normal peripheral zone between cases and controls. Significant difference in the mean HU was seen between the PSMA avid focus in cases (40.1 +/- 6.2) and normal peripheral zone of cases (28.2 +/- 7.0) and controls (27.7 +/- 5.8). No significant difference was found between the mean HU values of high-grade PCa and non-high-grade PCa. Receiver operating characteristic (ROC) curve analysis revealed a mean HU cut-off of >= 35 for detecting PCa with a sensitivity and specificity of 86% and 90%, respectively, between cases and controls (AUC 0.88). Conclusion: Detection of clinically significant PCa is possible on routinely performed NCCT scans. Radiologists should routinely look for and convey these findings to facilitate further work-up and early detection of PCa. Advances in knowledge: Our study adds to the knowledge that NCCT scans performed for unrelated indications can serve as a screening tool for clinically significant PCa.