Objective:

Positron emission tomography (PET) probes targeting prostate-specific membrane antigen (PSMA) have gained increasing interest, while the use of PSMA PET/computed tomography (CT) for prostate cancer (PCa) has rapidly and widely expanded over the last 5 years. The most preferred radiotracers available at many European PET centers, including those in Turkey, are 68Gallium (68Ga)-PSMA-11 and 68Ga-PSMA-I&T. The aim of this study is to compare 68Ga-PSMA-11 and 68Ga-PSMA-I&T PET/CT in patient groups with similar characteristics.

Methods:

PSMA PET/CT images of 81 patients with biopsy-proven PCa were retrospectively analyzed. Physiological distribution, tumor-to-background ratios, positivity rates, uptakes, and visual score classifications of primary tumors, lymph nodes, and bone metastases were analyzed for comparison. Additionally, PET/CT findings were compared according to the proposed molecular imaging tumor, node, and metastasis (miTNM) classification.

Results:

There was no significant difference between PSMA-11 and PSMA-I&T in terms of overall positivity rates, bone metastases, recurrent tumors, and overall detection rates of recurrent disease. Blood pool as well as bone marrow and muscle uptake of PSMA-I&T were slightly higher than those of PSMA-11. There was no significant difference between uptake values, tumor-to-background ratios, and visual scores of lymph node and bone metastasis. Average maximum standardized uptake values (SUVmax) and visual scores of primary tumors with PSMA-I&T were slightly higher than those of PSMA-11; however, the variance was minor, and there was no statistically significant difference between tumor-to-background ratios of primary tumors. Pelvic lymph node mapping according to the miTNM template showed similar results with both tracers.

Conclusion:

68Ga-PMSA-I&T may have an advantage with slightly higher uptake in primary tumors and slightly lower blood pool and bone marrow uptake. However, 68Ga-PMSA-I&T and 68Ga-PSMA- 11 showed similar clinical performance for staging and restaging of PCa in terms of detection rates, visual scores, tumor uptakes, and comparable physiological distribution.

Keywords: Positron emission tomography, prostate cancer, prostate specific membrane antigen