Prospective evaluation of ¹⁸F-PSMA-1007 PET/CT in renal masses paired with PSMA immunohistochemistry

Incidental renal masses (RM) are increasingly detected with cross-sectional imaging, and 20-30% of resected small RM are benign, exposing patients to potentially unnecessary surgery. Improved preoperative characterization is needed. Prostate-Specific Membrane Antigen (PSMA) expression in tumor neovasculature enables functional assessment, and ¹⁸F-PSMA-1007 has lower renal elimination than ⁶⁸Ga-PSMA-11, potentially improving lesion conspicuity.

This was a prospective cross-sectional accuracy study including 24 adults with renal masses scheduled for nephrectomy. All underwent ¹⁸F-PSMA-1007 positron emission tomography/computed tomography (PET/CT) approximately 60 min post-injection. PET positivity was defined as uptake greater than splenic standardized uptake value maximum (SUVmax) or unequivocally positive uptake on visual assessment. PSMA immunohistochemistry (IHC) in tumor vasculature was graded as absent, mild, moderate, or marked.

Twenty-five RM were analyzed in 24 patients, all incidentalomas: 14 (56%) renal cell carcinomas (RCC) - 10 clear cell, 3 papillary, and 1 chromophobe - and 11 (44%) benign lesions.¹⁸F-PSMA-1007 PET/CT detected 10/14 RCC (sensitivity 71.4%) with specificity 54.5% for malignant versus benign discrimination; sensitivity was higher in clear cell RCC (80%) than papillary RCC (33.3%). PET uptake correlated with PSMA expression on IHC (p = 0.026). Mass size showed a linear association with PSMA expression; all lesions > 30 mm expressed PSMA on IHC, with marked expression in 54.5% versus 7.7% of lesions ≤ 30 mm. By contrast, SUVmax values overlapped between malignant and benign PET-positive lesions, and no robust SUV-based threshold emerged from this cohort.

¹⁸F-PSMA-1007 PET/CT showed concordance with PSMA immunohistochemistry and higher detectability in clear cell RCC, but its ability to distinguish malignant from benign renal masses was limited by modest specificity and overlap with benign oncocytic lesions. These findings support ¹⁸F-PSMA-1007 PET/CT as a complementary, not stand-alone, tool for selected cases of renal mass characterization.