Immunotherapy-related renal toxicity causes reversible renal enlargement

Purpose: Prior case reports have noted an increase in renal size and perinephric stranding accompanying immunotherapy-related renal toxicity due to checkpoint-inhibitor therapy. The purpose of this investigation was to systematically evaluate if immunotherapy-related renal toxicity affects renal size and possible associated imaging findings.

Methods: This retrospective multi-hospital study included 25 patients (13 men), mean age 67 years (range 46-83) who received immune-checkpoint inhibitors for cancer treatment, developed biopsy-proven immunotherapy-related nephritis, and who also had abdominal imaging before, during, and after nephritis was diagnosed. Long axis renal diameter, renal corticomedullary differentiation/enhancement and perinephric stranding were evaluated by two readers at three timepoints: (1) prior to checkpoint inhibitor therapy (baseline), (2) after biopsy-proven immunotherapy-related nephritis (post-treatment), and (3) following renal function recovery (follow-up). Intraclass correlation coefficient and Cohen's Kappa were calculated to quantify agreement. Logistic regression analysis was implemented to measure the association between each timepoint and imaging features.

Results: Reader agreement on kidney measurements was excellent (ICC = 0.87). There was an increase in renal size between baseline and post-treatment (p = 0.001), followed by a decrease between post-treatment to follow-up (p < 0.001). Agreement was perfect for abnormal renal corticomedullary differentiation/enhancement (Kappa = 1, p < 0.001) and almost perfect for perinephric stranding (Kappa = 0.97, p < 0.001). Neither post-treatment nor follow-up imaging findings were significantly associated with these findings compared to the baseline (p = 0.2-0.6).

Conclusion: Immunotherapy-related renal toxicity was associated with an increase in renal size coincident with acute renal dysfunction.