Radiologic features of immune checkpoint inhibitor-related nephritis with clinical correlation in biopsy-proven cases.

Abstract

e14585 Background: Radiologic findings associated with biopsy proven immune checkpoint inhibitor (ICI) related nephritis have not been described. The objective of this study is to describe the radiologic features of immunotherapy related nephritis on computerized tomography (CT) and positron emission tomography (PET). A secondary objective is to investigate the association of these radiologic features with renal outcomes. Methods: A retrospective review of all biopsy proven ICI-related nephritis between February 2017 and April 2021 was performed and 34 patients were identified. CT and PET-CT scans before the initiation of immune checkpoint inhibitors (baseline), at nephritis and after resolution of nephritis were reviewed. Total kidney volume, renal parenchymal SUVmax, renal pelvis SUVmax and blood pool SUVmean were obtained. Results: The total kidney volume was significantly higher at nephritis compared to baseline (464.7±96.8 mL vs. 371.7±187.7 mL; p < 0.001). Fifteen patients (44.1%) had > 30% increase in total kidney volume at nephritis. A > 30% increase in total kidney volume was associated with significantly higher renal toxicity grade (p = 0.007), higher peak creatinine level (p = 0.004) and more aggressive medical treatment (p = 0.011). New/increasing perinephric fat stranding was noted in 10 patients (29.4%) at nephritis. Among 8 patients with contrast-enhanced CT at nephritis, 1 patient (12.5%) developed bilateral wedge-shaped hypoenhancing cortical lesions that healed with focal scarring on subsequent scans. On PET-CT, the renal parenchymal SUVmax-to-blood pool SUVmean ratio was significantly higher at nephritis compared to baseline (2.13 vs. 1.68; p = 0.035). The renal pelvis SUVmax-to-blood pool SUVmean ratio was significantly lower at nephritis compered to baseline (3.47 vs. 8.22; p = 0.011). Conclusions: Bilateral increase in kidney size, new/increasing perinephric stranding and bilateral wedge-shaped hypoenhancing cortical lesions can occur in immunotherapy-related nephritis. On PET-CT, diffuse bilateral increase in radiotracer uptake throughout the renal cortex and decrease in radiotracer activity in the renal pelvis can be seen. A > 30% increase in total kidney volume was associated with significantly higher renal toxicity grade and more aggressive medical treatment in a subset of patients. Acknowledgment: National Institute of Health K01 Award (N.A.: K01AI163412).