The Diagnostic Value of Whole-Body HYNIC-PSMA 11 -Tc [99mTc] SPECT/CT scan in Early Staging of Patients with Moderate and High Risk Prostate Cancer

Objective: This prospective study aims to compare the diagnostic yield of conventional imaging modalities, including CT scan, bone scan, with ^99m Tc-HYNIC-PSMA-11, in detecting local and distant metastases for initial staging in treatment-naïve, intermediate- to high-risk prostate cancer (PCa) patients. ⁶⁸ Ga-PSMA or 18F-PSMA PET/CT scans are known as the preferred modalities for staging this kind of patients, but there are limited PET/CT facilities in developing countries. Methods & Materials: A total of 63 treatment-naïve PCa patients were included in the study for initial staging. Each patient underwent a chest and abdominopelvic CT scan, bone scan, and ^99m Tc-HYNIC-PSMA-11 imaging. ^99m Tc-HYNIC-PSMA-11 (20–25 mCi) and ^99m TC-MDP (20–25 mCi) were administered intravenously, and imaging was performed 3 to 4 hours post-injection. Nuclear scans included whole-body imaging with SPECT or SPECT/CT phases in two fields (thorax and abdominopelvic), along with imaging of suspicious areas. All images were independently interpreted and analyzed on a patient-based and region-based level. Results: Region-based analysis revealed osseous metastatic regions in 78 (median 0 per patient, range 0–9), 25, and 87 (median 2 per patient, range 0–9) regions in the PSMA-11 scan, CT scan, and bone scan, respectively. CT scan was limited in assessing all nine osseous regions due to its restricted field of view. The positive detection rate for local lymph node and distant metastases (distant lymphatic, osseous, and visceral) was 18/63 (28.6%) and 23/63 (41.3%) for the PSMA-11 scan, and 20/63 (31.8%) and 27/63 (42.9%) for the CT scan, with no significant difference between the two modalities. Overall, the combined findings of the PSMA-11 scan, CT scan, and bone scan were positive in 31/63 (49.2%), 34/63 (53.9%), and 32/63 (50.8%) patients, respectively. Equivocal findings were reported in 1 PSMA-11 scan, 13 CT scans, and 4 bone scans. When equivocal findings were considered as positive for metastasis, the accuracy, sensitivity, and specificity were 78.2%, 60%, and 96.4% for the PSMA-11 scan; 76.1%, 62.9%, and 89.3% for the CT scan; and 85%, 78.6%, and 91.4% for the bone scan. There was a strong agreement in disease staging and overall findings between the PSMA-11 scan and the combination of CT and bone scans (Ƙ = 0.949 and Ƙ = 0.905, respectively; p < 0.001). Conclusion: The comparable accuracy and high concordance between ^99m Tc-HYNIC-PSMA-11and conventional CT and bone scans make ^99m Tc-HYNIC-PSMA-11 an effective method for initial staging of intermediate- to high-risk prostate cancer patients.