Comparing 99mTc-PSMA to 99mTc-MDP in Prostate Cancer Staging of the Skeletal System

This prospective study was aimed at assessing the ability of 99mTc-PSMA scan to detect bone metastases in prostate cancer (PCa) against 99mTc-MDP scan as a standard and assess the correlation of these modalities in PCa staging of bone involvement.

Forty-one patients (41) with histologically confirmed PCa were scanned using both methods. Planar imaging was performed with additional regional SPECT/CT 3 to 4 hours posttracer injection. Scans were reported as positive, negative, or equivocal. In the case of positive scans, lesions were quantified by each of the 3 reporters separately. Planar and SPECT/CT images were reported together to obtain the final report on each scan.

Our preliminary results showed no significant difference in the detection of bone metastases between the 2 scans. 99mTc-PSMA detected 52 of the 55 bone lesions detected on 99mTc-MDP. However, 99mTc-PSMA provided extra information by reporting lymph nodal metastases in 7 patients and residual disease in the prostate in 2 patients with biochemical progression after radical therapy. In 1 patient, the PSMA scan resulted in change in management with patient now on 177Lu-PSMA radioligand therapy. Equivocal findings were reported in 4 patients on 99mTc-MDP and none on 99mTc-PSMA.

99mTc-PSMA was comparable to 99mTc-MDP in detection of bone metastases and demonstrated an additional benefit of providing information on visceral disease. 99mTc-PSMA may be a better alternative to 99mTc-MDP in staging, restaging, and assessment of patients with biochemical progression after radical therapy of PCa in a resource-limited setup like ours while also assisting to detect patients eligible for PSMA-labeled radioligand therapy.