Biomarkers, Clinical Features, and Rechallenge for Immune Checkpoint Inhibitor Renal Immune-Related Adverse Events.

Introduction: Immune checkpoint inhibitors (ICIs) are effective in treating several cancers; however, acute kidney injury (AKI) can occur as part as an immune-related adverse event (iRAE). Biomarkers at the time of AKI diagnosis may help determine whether they are ICI- related and guide therapeutic strategies.

Methods: In this retrospective study, we reviewed patients with cancer treated with ICI therapy between 2014 and 2020 who developed AKI (defined as a ≥1.5-fold increase in serum creatinine [SCr]) that was attributed to ICI (ICI-AKI) and compared them with an adjudicated non-ICI-AKI group. Clinical and laboratory features, including SCr, serum C-reactive protein (CRP), and urine retinol binding protein/urine creatinine (uRBP/Cr) levels at AKI event were evaluated.

Results: There were 37 patients with ICI-AKI and 13 non-ICI-AKI referents in the cohort for analysis. At time of AKI, SCr, CRP, and uRBP/Cr were significantly higher in the ICI-AKI compared with the non-ICI-AKI patients (median [interquartile range (IQR)] SCr 2.0 [1.7, 2.9] vs. 1.5 [1.3, 1.6] mg/dl, serum CRP 54.0 [33.7, 90.0] vs. 3.5 [3.0, 7.9] mg/l, and uRBP/Cr 1927 [1174, 46,522] vs. 233 [127, 989] μg/g Cr, respectively,  < 0.05 for all). Compared with the referent group, time from ICI initiation to AKI was shorter in the ICI-AKI patients. Among the ICI-AKI group, complete renal recovery occurred in 39% of patients by 3 months; rechallenge occurred in 16 (43%) of patients, of whom 3 (19%) had recurrence of AKI.

Conclusion: Our findings suggest that serum CRP and uRBP/Cr may help to differentiate AKI due to ICI from other causes.