89Zr-girentuximab PET/CT Enables Noninvasive Assessment of Indeterminate Renal Masses and Metastatic Clear-Cell Renal Cell Carcinoma.

Background

Indeterminate renal masses (IRMs) frequently require biopsy for characterization and often lead to unnecessary surgical interventions. 89Zr-girentuximab is a positron emission tomography (PET) radiopharmaceutical targeting carbonic anhydrase IX, a biomarker overexpressed in clear-cell renal cell carcinoma (ccRCC). This real-world experience demonstrates the impact of 89Zr-girentuximab PET on the clinical management of patients with IRM and its role in differentiating primary and metastatic ccRCC from other etiologies.

Methods

This prospective single-center study, part of an expanded access program (NCT06090331), investigated patients with IRM on conventional imaging who underwent 89Zr-girentuximab PET/computed tomography (PET/CT). Qualitative and quantitative PET/CT features of each lesion were assessed. Pathologic or clinical diagnosis was determined for all lesions. Referring physicians were surveyed to evaluate the impact of PET on patient management.

Results

Seven male patients (age range, 57-78 years) were included; four had ccRCC (including two with metastatic disease) and three had oncocytoma (including one with Birt-Hogg-Dubé syndrome). Across all 32 lesions identified, 89Zr-girentuximab PET/CT accurately characterized each lesion based on pathologic or clinical diagnosis. 89Zr-girentuximab PET/CT identified ccRCC tumor thrombi in the inferior vena cava and renal vein branches (SUVmax 12.0-13.0), a perinephric deposit (SUVmax 36.4), and intramuscular (SUVmax 103.0), pulmonary (SUVmax 4.0-10.5), and osseous (SUVmax 10.2) metastases. 89Zr-girentuximab PET/CT enabled the diagnosis of oncocytomatosis in one patient and detected a renal lesion with positive uptake that was occult on MRI. According to referring physicians, 89Zr-girentuximab PET/CT changed clinical management in six of seven patients and improved patient care in all cases.

Conclusions

89Zr-girentuximab PET/CT provides a noninvasive tool for characterizing indeterminate renal masses and metastatic ccRCC and may improve clinical problem-solving in complex scenarios.