Time-dependent recovery of renal impairment in patients with newly diagnosed multiple myeloma

Renal impairment is reported in 20%-50% of patients with newly diagnosed multiple myeloma and is known as a poor prognostic factor. Although several studies have demonstrated that treatment with novel antimyeloma agents improves renal impairment and myeloma itself, the time-dependent clinical course of recovery of renal function has not been extensively studied. We retrospectively collected the data of characteristics and outcomes in consecutive unselected patients diagnosed with and treated for symptomatic multiple myeloma between January 2015 and December 2022, and extracted and analyzed the cases with renal impairment. Among 234 patients with multiple myeloma, 67 (28.6%) had renal impairment (estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73m²) at the time of diagnosis. The median eGFR at diagnosis was 28 ml/min/1.73m², and the eGFR significantly improved to 41.5 ml/min/1.73m², which corresponds to a 42.9% increase, at 3 months after the initiation of treatment for myeloma (p < 0.0001). Further improvement in renal function was not observed at 6 months (eGFR 46 ml/min/1.73m²) and 1 year (eGFR 43.5 ml/min/1.73m²) after treatment initiation. The primary treatment was a bortezomib-containing regimen in approximately 90% of patients. A post hoc analysis revealed a positive correlation between the serum calcium concentration at diagnosis and improvement in renal function. In conclusion, renal function can partially recover through the treatment of multiple myeloma, and the treatment response during the first 3 months may predict the renal function prognosis. Further accumulation of cases is needed to identify the predictive factors for renal recovery.