Potential role of ⁶⁸Ga-PSMA PET/CT in metastatic renal cell cancer: A prospective study

Purpose: Prostate-specific membrane antigen (PSMA), in addition to its utility in prostate cancer, is also an angiogenic imaging marker for hypervascular tumors like renal cell carcinoma (RCC). Our study aims to assess the potential role of Ga-68-PSMA-11 positron emission tomography (PET)/CT in metastatic RCC and compare it with contrast-enhanced computed tomography (CECT).Methods: Biopsy-proven RCC patients with known or suspected distant metastases who underwent Ga-68-PSMA-11 PET/CT for staging/restaging were prospectively recruited. Those patients who had undergone F-18-FDG PET/CT within six weeks of Ga-68-PSMA PET/CT were also included retrospectively for comparative analysis. A patient-based and lesion-based analysis was done to compare the lesion detection rates of CECT, Ga-68-PSMA-11 PET and F-18-FDG PET. PET-based quantitative parameters were also compared between both the PET modalities. Impact of baseline parameters on survival was assessed using Cox regression analysis. A p-value of < 0.05 was considered significant.Results: Thirty-seven patients with median age 60 years +/- 13 years (range = 26-76 years) were included in the study. Twenty-seven patients had clear cell (cc) RCC, six had papillary RCC (pRCC), and one each had an eosinophilic variant of ccRCC, collecting duct RCC, translocation RCC and poorly differentiated RCC. Ga-68-PSMA-11 PET performed better in detecting marrow and equivocal bone lesions and worse in detecting liver lesions compared to CECT. Ga-68-PSMA-11 PET-based angiogenic tumor burden estimation using Total Lesion-PSMA (TL-PSMA) and PSMA-Total volume (PSMA-TV) had a prognostic impact on the survival of patients. Ga-68-PSMA-11 PET also detected more lesions and showed significantly higher SUVmax than F-18-FDG PET.Conclusion: Ga-68-PSMA-11 PET/CT performs better than CECT and F-18-FDG PET/CT in metastatic evaluation and has prognostic value in the management of clear cell RCC.