Kidney outcomes and prognostic factors of myeloma associated acute kidney injury in the contemporary era

Myeloma cast nephropathy (MCN) has historically been associated with poor kidney outcomes. We aimed to evaluate the kidney outcomes and identify prognostic factors of myeloma-associated acute kidney injury (M-AKI) in the contemporary era of anti-plasma cell therapy. Patients who received anti-myeloma therapy with M-AKI (January 2012 to June 2020) from a single centre were identified from electronic medical records. Diagnosis of MCN was either biopsy confirmed (BC) or clinically suspected (CS), the latter defined as acute kidney injury with reduced estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m(2) and involved serum free light chains (iSFLC) >500 mg/L at diagnosis. Twenty-six patients with M-AKI were identified (BC: n = 13, CS: n = 13). Median eGFR at diagnosis was 12 (interquartile range 6-20) mL/min/1.73 m(2). All six dialysis-requiring patients achieved dialysis independence after 71 (43-208) days. The best-achieved eGFR was 47 (32-67) mL/min/1.73 m(2) after 120 (63-167) days post-treatment, which was maintained at 47 (33-66) mL/min/1.73 m(2) 12 months post-treatment. Patients with best-achieved eGFR above the median were more likely to have achieved an iSFLC of <20 mg/L (above median group 62% versus below median group 0%; p < .001) and lower best post-treatment iSFLC (20 (12-90) versus 67 (29-146) mg/L; p < .05). Best-achieved iSFLC was a prognostic factor for superior eGFR following treatment for M-AKI. Despite low eGFR at diagnosis, contemporary anti-myeloma therapy can achieve significant recovery of kidney function.