Planar Tc-PSMA Imaging of Prostate Cancer in a Low-Resource Setting: A Series Report.

Technetium-99m labeled prostate-specific membrane antigen (PSMA) single-photon emission computed tomography/computed tomography (SPECT/CT) is a suitable alternative to prostate-specific membrane antigen-positron emission tomography (PSMA-PET) imaging. However, the availability of SPECT/CT in many developing countries is limited.  To evaluate the utility of planar Tc-PSMA in the absence of SPECT/CT, we compared planar Tc-PSMA and routine bone scan imaging in low-, intermediate-, and high-risk prostate cancer in five patients with histologically confirmed prostate cancer who had both scans within a period of less than 4 days. The mean age of patients was 66.8 ± 5.24, and the median prostate-specific antigen level was 175 ng/mL (range: 0-778 ng/mL).  Planar Tc-PSMA scan provided no additional benefit over bone scans in the low-risk prostate cancer cases. In the cases with intermediate-risk prostate cancers, planar Tc-PSMA indicated complete and partial response to treatment in oligometastatic and widespread metastatic disease, respectively. In one patient with high-risk prostate cancer, planar Tc-PSMA detected additional skeletal lesions that were not seen on bone scan.  In the absence of SPECT/CT, planar Tc-PSMA was useful for confirming extent of disease in treated intermediate- and high-risk prostate cancer. It showed little value in low-risk prostate cancer, especially when bone scan is normal. It was particularly useful for treatment response assessment in oligometastatic disease, and its utility should be further explored.