Practice-Changing Data on Novel Noninvasive Imaging Modality for Detection of Clear-Cell RCC

[⁸⁹Zr]Zr-girentuximab PET-CT has a favorable safety profile and is a highly accurate noninvasive imaging modality for the detection and characterization of clear-cell renal cell carcinoma (RCC), according to ZIRCON trial data.

ZIRCON was a prospective, open-label, multicenter, phase 3 trial that included patients aged 18 years or older with an indeterminate renal mass ≤7 cm suspicious for clear-cell RCC and scheduled for nephrectomy.

A team of researchers, led by Brian Shuch, MD, randomly assigned 300 patients (214 [71%] male; 86 [29%] female), of whom, 284 (95%) were evaluable patients and included in the primary analysis, to receive a single dose of ⁸⁹Zr intravenously five days before abdominal PET-CT imaging, with surgery performed no later than 90 days after ⁸⁹Zr administration.

The coprimary endpoints, determined for each individual, were the sensitivity and specificity of ⁸⁹Zr PET-CT imaging for renal masses ≤7 cm. Key secondary endpoints were the sensitivity and specificity of ⁸⁹Zr in renal masses ≤4 cm. Sensitivity was defined as the proportion of patients with a true-positive ⁸⁹Zr PET-CT relative to those with a positive clear-cell RCC histopathological diagnosis. Specificity was defined as the proportion of patients with a true-negative ⁸⁹Zr PET-CT (no clear-cell RCC), relative to those with a negative histopathological diagnosis.

For all evaluable patients (n=284), mean sensitivity for all imaging readers was 85.5% (95% CI, 81.5-89.6), and mean specificity was 87% (95% CI, 81.0-93.1). No safety concerns were associated with administration, which is consistent with published literature. The most common severe adverse events (grade 3 or higher), each with one event per person, were post-procedural hemorrhage (2%), urinary retention (1%), and hypertension (1%).

This method of imaging “was consistent in patients irrespective of smaller size of indeterminate renal mass,” the researchers concluded, noting that ⁸⁹Zr imaging has “the potential to be practice changing.”