Immune Checkpoint Inhibitor-Associated Acute Kidney Injury: A Single-Center Experience of Biopsy-Proven Cases

<b>Background</b>: Immune checkpoint inhibitor therapy (ICI) has greatly changed cancer therapy in recent years. The main side effects are immune-related adverse events (irAEs) that can affect any organ system. With the widespread use of ICIs, even rare irAEs, like acute kidney injury due to ICI-induced nephritis (ICI-AKI), have become a more common complication. <b>Methods</b>: All ICI-treated patients who underwent a kidney biopsy for AKI at a single academic center between January 2020 and December 2023 were analyzed. <b>Results</b>: We identified twelve cases of biopsy-proven ICI-AKI. The median follow up was 11.5 months. All cases showed acute interstitial nephritis (AIN) on the biopsy. Melanoma was the most common cancer, and dual-checkpoint inhibition with Ipilimumab and Nivolumab was the most common regimen. Extrarenal irAEs were present in only 25% of cases. Two-thirds had concomitant medication with proton pump inhibitors (PPIs). Only four patients completely recovered their kidney function, and one patient remained on kidney replacement therapy. <b>Conclusions</b>: AIN is a common cause of AKI in ICI-treated cancer patients. Although they respond well to steroid treatment, full restitution of kidney function occurs in less than half of the subjects. As ICIs are increasingly used in cancer management, more research on the prevention and treatment of ICI-associated AKI is needed.