A prospective comparative study of 68Ga-RM26 and 68Ga-PSMA-617 PET/CT imaging in suspicious prostate cancer

Abstract

Abstract Purpose Prostate-specific membrane antigen (PSMA) -based PET/CT imaging showed limitations in the diagnosis of prostate cancers (PCa). We recruited 207 participants with suspicious PCa to perform PET/CT imaging with radiolabeled gastrin-releasing peptide receptor (GRPR) antagonist, 68Ga-RM26, and compare with 68Ga-PSMA-617 and histopathology. Methods Participants with suspicious PCa were subjected to 68Ga-RM26 and 68Ga-PSMA-617 PET/CT. PET/CT imaging was compared using pathologic specimens as a reference standard. Results Of the 207 participants analyzed, 125 had cancer, and 82 were diagnosed with benign prostatic hyperplasia (BPH). The sensitivity and specificity of 68Ga-RM26 and 68Ga-PSMA-617 PET/CT imaging differed significantly for detecting clinically significant prostate cancer (csPCa). The area under the ROC curve (AUC) was 0.54 for 68Ga-RM26 PET/CT and 0.91 for 68Ga-PSMA-617 PET/CT detecting PCa. For csPCa imaging, the AUCs were 0.51 vs. 0.93, respectively. However, 68Ga-RM26 PET/CT imaging had higher sensitivity for PCa with Gleason Score (GS) =6 (p=0.03) than 68Ga-PSMA-617 PET/CT but poor specificity (20.73%). In the group with PSA <10 ng/mL, the sensitivity, specificity, and AUC of 68Ga-RM26 PET/CT were lower than 68Ga-PSMA-617 PET/CT (60.00% vs. 80.30%, p=0.12, 23.26% vs. 88.37%, p=0.000, and 0.524 vs. 0.822, p=0.000, respectively). 68Ga-RM26 PET/CT exhibited a significantly higher SUVmax in specimens with GS=6 (p=0.04) and in the low-risk group (p=0.01), and its uptake did not increase with the PSA level, GS, or clinical stage. Conclusion This prospective study provided evidence for superior accuracy of 68Ga-PSMA-617 PET/CT over 68Ga-RM26 PET/CT in the detection of csPCa. And 68Ga-RM26 PET/CT showed an advantage for imaging of low-risk PCa.