Comparative analysis of PSMA PET-CT: Assessing prostate cancer activity without CT findings

BACKGROUND/OBJECTIVE: Prostate cancer (PCa) is a prevalent malignancy globally, especially in developed nations. Timely diagnosis and treatment are crucial for survival, with higher rates in developed countries. ⁶⁸ Ga-PSMA PET-CT aids in identifying metastatic disease, guiding personalized treatment strategies. The aim of this study is to compare the uptake of the radiotracer ⁶⁸ Ga-PSMA in primary and metastatic prostate cancer lesions identified on PSMA PET-CT against conventional CT (Computed Tomography) in staging prostate cancer patients. METHODS A retrospective, cross-sectional study was conducted in the PET-CT Unit. Seventy-one patients diagnosed with prostate cancer by histopathology who underwent PSMA PET-CT scan and who were referred for CT staging were included. The study variables were the determination of the maximum standardized uptake value (SUVmax), and the anatomic location of lesions detected by ⁶⁸ Ga-PSMA in bone, lymph node, prostate, and lung. Lesions were classified as seen by PSMA PET-CT or by both PSMA PET-CT and conventional Computed Tomography. RESULTS A total of 113 lesions of tumoral activity were identified: 70 lesions were detected only with ⁶⁸ Ga-PSMA PET-CT with a mean SUVmax of 14.14 ± 11.25, in contrast to a mean SUVmax of 23.15 ± 20.51 in 43 lesions detected by both PSMA PET-CT and conventional CT. (p = 0.049). CONCLUSION Positive ⁶⁸ Ga-PSMA PET-CT showed metastatic disease that otherwise would have not been diagnosed in patients undergoing conventional CT, which corresponds to an upstaging in 67% of patients. These results are relevant due to the limited availability of PET-CT equipment in global south countries.