Head-To-Head Comparison of 68Ga-PSMA-11 PET/CT and 99mTc-MDP Bone Scintigraphy for the Detection of Bone Metastases in Patients With Prostate Cancer: A Meta-Analysis

BACKGROUND. Bone scintigraphy (BS) using Tc-99m-labeled methylene diphosphonate (Tc-99m-MDP) remains the recommended imaging modality for the detection of bone metastases in patients with prostate cancer (PCa). However, PET/CT using prostate-specific membrane antigen (PSMA) ligands is increasingly recognized as a means of evaluating disease extent in patients with PCa, including use as a possible stand-alone test in high-risk patients. OBJECTIVE. The purpose of this study is to compare the diagnostic performance of Ga-68-PSMA-11 PET/CT with that of Tc-99m-MDP BS for the detection of bone metastases in patients with PCa. EVIDENCE ACQUISITION. The PubMed, Embase, and Cochrane Library databases were searched through October 2021 to identify studies reporting a head-to-head comparison of Ga-68-PSMA-11 PET/CT and Tc-99m-MDP BS for the detection of bone metastases in patients with PCa. Only studies with a well-defined reference standard (including various combinations of imaging and/or clinical follow-up) were included. Pooled diagnostic performance was calculated using a bivariate random-effects model, and an AUC was derived for each test from hierarchic summary ROC analysis. The complementary roles of the two tests in identifying bone metastases in patients in whom one of the tests was negative were summarized. EVIDENCE SYNTHESIS. Six studies with 546 patients were included. Pooled sensitivity and specificity, respectively, were 98% (95% CI, 94-99%) and 97% (95% CI, 91-99%) for Ga-68-PSMA-11 PET/CT versus 83% (95% CI, 69-91%) and 68% (95% CI, 41-87%) for Tc-99m-MDP BS. The AUC was 0.99 (95% CI, 0.96-1.00) for Ga-68-PSMA-11 PET/CT and 0.85 (95% CI, 0.81-0.87) for Tc-99m-MDP BS. Among 408 patients from five included studies, Ga-68-PSMA-11 PET/CT correctly identified bone metastases in 43 of 193 patients (22.3%) with negative Tc-99m-MDP BS results, whereas Tc-99m-MDP BS correctly identified bone metastases in four of 210 patients (1.9%) with negative Ga-68-PSMA-11 PET/CT results. CONCLUSION. On a per-patient basis, the diagnostic performance of Ga-68-PSMA-11 PET/CT is superior to that of Tc-99m-MDP BS for the detection of PCa bone metastases. Furthermore, Tc-99m-MDP BS offers limited additional information in patients with negative Ga-68-PSMA-11 PET/CT results. CLINICAL IMPACT. According to current evidence, Tc-99m-MDP BS is highly unlikely to be additive to Ga-68-PSMA-11 PET/CT in identifying bone metastases in patients with PCa.