Positron emission tomography/computed tomography identification of clear cell renal cell carcinoma: Results from the REDECT trial

Purpose: A clinical study to characterize renal masses with positron emission tomography/computed tomography (PET/CT) was undertaken. Patients and Methods: This was an open-label multicenter study of iodine-124 ( ¹²⁴I) -girentuximab PET/CT in patients with renal masses who were scheduled for resection. PET/CT and contrast-enhanced CT (CECT) of the abdomen were performed 2 to 6 days after intravenous ¹²⁴I-girentuximab administration and before resection of the renal mass(es). Images were interpreted centrally by three blinded readers for each imaging modality. Tumor histology was determined by a blinded central pathologist. The primary end points-average sensitivity and specificity for clear cell renal cell carcinoma (ccRCC)-were compared between the two modalities. Agreement between and within readers was assessed. Results: ¹²⁴I-girentuximab was well tolerated. In all, 195 patients had complete data sets (histopathologic diagnosis and PET/CT and CECT results) available. The average sensitivity was 86.2% (95% CI, 75.3% to 97.1%) for PET/CT and 75.5% (95% CI, 62.6% to 88.4%) for CECT (P = .023). The average specificity was 85.9% (95% CI, 69.4% to 99.9%) for PET/CT and 46.8% (95% CI, 18.8% to 74.7%) for CECT (P = .005). Inter-reader agreement was high (κ range, 0.87 to 0.92 for PET/CT; 0.67 to 0.76 for CECT), as was intrareader agreement (range, 87% to 100% for PET/CT; 73.7% to 91.3% for CECT). Conclusion: This study represents (to the best of our knowledge) the first clinical validation of a molecular imaging biomarker for malignancy. ¹²⁴I-girentuximab PET/CT can accurately and noninvasively identify ccRCC, with potential utility for designing best management approaches for patients with renal masses.