EAU 2026: Impact of 89Zr-girentuximab PET Versus Conventional Imaging on Clinical Decision-making in Patients with Indeterminate Renal Masses (ZIRCON-X)

(UroToday.com) The European Association of Urology (EAU) 2026 Annual Congress was host to a renal cell carcinoma abstract session. Dr. David Liu presented results from ZIRCON-X, a post-hoc analysis of the phase 3 ZIRCON study evaluating the potential impact of 89Zr-girentuximab PET imaging on clinical management decisions for patients presenting with indeterminate renal masses (IRMs).

The phase 3 ZIRCON trial (NCT03849118) previously demonstrated that ⁸⁹Zr-girentuximab PET imaging provides high diagnostic accuracy for the detection, localization, and characterization of clear cell renal cell carcinoma (ccRCC).¹ By enabling more precise molecular imaging of renal masses, this approach has the potential to improve diagnostic certainty, support clinical decision-making, and potentially reduce the need for unnecessary biopsies or invasive procedures.

ZIRCON-X was designed as a post-hoc analysis of imaging data collected in the ZIRCON trial to evaluate how the incorporation of ⁸⁹Zr-girentuximab PET imaging could influence clinical management strategies for patients with indeterminate renal masses.

ZIRCON-X was conducted as a non-interventional post-hoc analysis utilizing imaging data obtained from the ZIRCON study. The eligibility criteria for ZIRCON have been previously published.¹

Four independent multidisciplinary teams (MDTs), each composed of urologists and nuclear medicine physicians from separate institutions, evaluated patient cases to determine clinical management strategies. These decisions were made using available clinical and laboratory data through a two-step process.

• In Step 1, MDTs reviewed conventional imaging (CI), consisting of CT and/or MRI, and proposed a clinical management plan based solely on these data.
• In Step 2, conducted at least four weeks later to minimize recall bias and preserve the integrity of comparisons, MDTs reassessed each case after reviewing the ⁸⁹Zr-girentuximab PET/CT images. During this second review, teams were permitted to re-examine the original CT/MRI images but were blinded to their prior Step 1 decisions.

Throughout both steps, MDTs had access to clinical and laboratory information but remained blinded to patient histopathology and to the actual management decisions made in the original ZIRCON trial.

The primary endpoints of the analysis included the proportion of patients whose clinical management plan would change after incorporation of ⁸⁹Zr-girentuximab PET imaging compared with conventional imaging alone, as well as hypothetical major and minor management changes attributable to PET findings.

A total of 294 patients were included in the analysis. Overall, incorporation of ⁸⁹Zr-girentuximab PET imaging would have resulted in a change in clinical management in 143 of 294 patients (48.6%) compared with decisions based on conventional imaging alone.

Major changes in management would have occurred in 110 of 294 patients (37.4%). These included several clinically meaningful shifts in treatment strategy:

• 24 of 110 patients (21.8%) would have shifted from biopsy to surgery
• 19 of 110 patients (17.3%) would have shifted from surgery to biopsy
• 18 of 110 patients (16.4%) would have shifted from additional diagnostic evaluation to surgery
• 8 of 110 patients (7.3%) would have changed from partial nephrectomy to radical nephrectomy
• 7 of 110 patients (6.4%) would have shifted from surgery to additional diagnostic evaluation
• 6 of 110 patients (5.5%) would have changed from radical to partial nephrectomy

Minor changes in management were observed in 33 of 294 patients (11.2%). These modifications included:

• 10 of 33 patients transitioning from additional diagnostic evaluation to active surveillance
• 7 of 33 patients transitioning from active surveillance to further diagnostic testing
• 4 of 33 patients moving from additional diagnostic evaluation directly to treatment

Beyond these management changes, the addition of ⁸⁹Zr-girentuximab PET imaging also increased multidisciplinary team confidence in clinical decision-making. MDT confidence in the management plan improved for 93 of 294 patients (31.6%) compared with conventional imaging alone.

Dr. Liu concluded that results from the ZIRCON-X analysis suggest that incorporation of ⁸⁹Zr-girentuximab PET imaging could substantially influence the clinical management of patients presenting with indeterminate renal masses.

Nearly half of the patients in this study would have experienced a change in their proposed management strategy after PET imaging results were considered. These findings highlight the potential clinical utility of CAIX-targeted PET imaging in improving diagnostic certainty and guiding treatment decisions in patients with small renal masses.

Importantly, this imaging approach may support both escalation and de-escalation of treatment strategies, helping clinicians better select patients for biopsy, surgery, or active surveillance while potentially reducing unnecessary invasive interventions.

Presented by: David Liu, MD, Chief Medical Officer, Telix Pharmaceuticals, Department of Medical Affairs, North Melbourne, Australia

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 EAU 2026 Annual Congress, London, UK, March 13th–16th, 2026

1. 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.