Comparison of Ga 68 PSMA-11 and F 18 Choline for detection of prostate cancer during biochemical relapse

Abstract

Prostate Cancer (PCa) is the most common cancer in men. In 2020, there were 1.4 million new cases and 375,000 deaths worldwide. The most important biomarker for PCa is the prostate-specific antigen (PSA), which is helpful for the initial screening, detection, and follow-up after surgery. Serum PSA level is also used as a sensitive marker for tumor recurrence. Any increase in PSA level during the follow-up period after the complete prostatectomy procedure is interpreted as a biochemical cancer relapse. Since 15-30% of patients experience a biochemical relapse after curative treatment of radical prostatectomy (RP) or radiation therapy, the development of new technologies and therapeutic strategies for diagnosing and treating PCa biochemical relapse is of major significance. The objective of the current study was to assess the utility of Ga 68 PSMA-11 (a target molecule and inhibitor of the prostate-specific membrane antigen), and F 18 Choline (a molecule that increases in level along with increases in cancer cells) in identifying biochemical relapse of PCa. The U. S. Food and Drug Administration (FDA) has approved Gallium 68 PSMA-11 (Ga 68 PSMA-11) as the first marker for detecting PSMA-positive lesions in men with PCa in the United States. Our study was based on anonymized data from the Clinical Physiology and Nuclear Medicine Unit of the Helsinki University Hospital (HUS) in Finland. A total of 199 participants examined from January 2015 to June 2016 were included in this study. Positron Emission Tomography-Computed Tomography (PET/CT) imaging was used as the gold standard. Cross-tabulation tables were constructed to assess the performance (sensitivity, specificity, and overall accuracy, with respective 95% confidence intervals [95% CI]) of both diagnostic tests (based on Ga 68 PSMA-11 and F 18 Choline) in detecting biochemical relapse of PCa among patients with PSA > 2 µg/L. The screening test using F 18 Choline had a specificity of 92.9% (95% CI 83.0% - 98.1%), and an overall accuracy of 93.1% (95% CI 83.3% - 98.1%). The screening test using Ga 68 PSMA-11 had a specificity of 59.6% (95% CI 44.3% - 73.6%), and an overall accuracy of 60.4% (95% CI 45.3% - 74.2%). For both markers, we did not report sensitivity since the 95% CIs had a wide range (95% CI 2.5% - 100.0%). Further investigations are necessary to investigate the sensitivity of these diagnostic tests. Our results did not agree with previous reports of better sensitivity and specificity for Ga 68 PSMA-11, compared with F 18 Choline. While we were unable to compare the two markers directly due to HUS regulations, the current study demonstrated that Ga 68 PSMA-11 can be used in HUS settings to detect PCa in patients with biomedical relapse. Future studies of Ga 68 PSMA-11, particularly those that perform direct comparisons with other diagnostic tests, are needed.