(UroToday.com) The European Association of Urology (EAU) 2026 Annual Congress was host to a renal cell carcinoma abstract session. Dr. Huebner-Resch presented her team’s initial real-world experience using [89Zr]Zr-girentuximab PET/CT in the routine evaluation of patients with indeterminate renal masses.
The PET tracer [89Zr]Zr-girentuximab targets carbonic anhydrase IX (CAIX), a hypoxia-inducible enzyme that is strongly expressed in clear cell renal cell carcinoma (ccRCC). CAIX expression is highly characteristic of ccRCC, making it an attractive biomarker for non-invasive tumor characterization.
Evidence supporting this approach was previously demonstrated in the multicenter, open-label phase III ZIRCON trial, which enrolled 284 adult patients. In that study, [89Zr]Zr-girentuximab PET/CT demonstrated high diagnostic accuracy in differentiating ccRCC from other benign and malignant renal lesions. Building on these findings, the investigators sought to evaluate the performance of this imaging modality in a real-world clinical setting among patients with renal masses of uncertain origin.
Within an early access program, patients presenting with renal lesions of indeterminate origin underwent imaging with [89Zr]Zr-girentuximab PET/CT as part of their diagnostic work-up. Each participant received an intravenous injection of 37 MBq (±10%) of [89Zr]Zr-girentuximab, followed by PET/CT imaging performed approximately five days after tracer administration (day 5 ±2 days).
A total of 22 patients were included in the analysis, comprising 15 men and 7 women, with a mean age of 71 ± 9 years. Across these patients, 26 renal lesions of uncertain etiology were evaluated. Final histopathologic confirmation was available in a subset of 10 patients.
The radiotracer demonstrated an excellent safety profile. [89Zr]Zr-girentuximab PET/CT was well tolerated across all patients, with no adverse events or unexpected reactions reported.
Among four patients (five lesions) demonstrating markedly increased CAIX expression on PET imaging—with maximum standardized uptake values (SUVmax) reaching up to 40—histopathologic evaluation confirmed clear cell renal cell carcinoma in all cases. Within this subset of patients with available pathology, the imaging modality achieved a sensitivity and specificity of 100% for detecting ccRCC.
In contrast, PET/CT scans in the remaining six patients with available histopathology were visually negative for CAIX expression. All six lesions in this group represented true-negative findings. Final diagnoses included oncocytoma (n = 3), angiomyolipoma (n = 1), papillary renal cell carcinoma (n = 1), and normal renal parenchyma (n = 1).
Importantly, the use of [89Zr]Zr-girentuximab PET/CT influenced downstream clinical management in a substantial proportion of cases. Overall, imaging results led to a change in treatment strategy in 12 of 22 patients (55%).
In nine patients, the imaging findings supported a conservative management approach with active surveillance, thereby avoiding potentially unnecessary surgery or systemic therapy. Among the 10 patients with available histopathologic confirmation, treatment decisions were altered in four cases based on PET/CT findings.
Dr. Huebner-Resch concluded as follows:
- This early real-world experience supports the high diagnostic performance and clinical value of [89Zr]Zr-girentuximab PET/CT in distinguishing clear cell renal cell carcinoma from benign renal tumors and non–clear cell histologies.
- These findings highlight the potential of CAIX-targeted PET imaging to improve diagnostic confidence, inform individualized treatment strategies, and reduce unnecessary invasive procedures in patients with indeterminate renal masses.
Presented by: Irene Huebner-Resch, MD, Department of Urology, Medical University of Vienna, Vienna, Austria
Written by: Rashid K. Sayyid, MD, MSc, Assistant Professor, Urologic Oncologist, Department of Urology at The University of Arizona and Banner University Medical Center, Tucson, AZ – @rksayyid on X during the 2026 European Association of Urology (EAU) Annual Meeting, London, United Kingdom, Fri, Mar 13 – Mon, Mar 16, 2026.
References:
- Schuch B, Pantuck AJ, Bernhard JC, et al. [89Zr]Zr-girentuximab for PET–CT imaging of clear-cell renal cell carcinoma: a prospective, open-label, multicentre, phase 3 trial. Lancet Oncol. 2024;25(10):1277-87.