Serum free light chain levels and renal function at diagnosis in patients with multiple myeloma

Abstract

Abstract Background Renal impairment (RI) is common in multiple myeloma (MM) and is associated with poor survival. This study reports the associations between renal function and disease characteristics including serum free light chain (FLC) level at diagnosis in patients with MM. Methods Using data from the Medical Research Council Myeloma IX trial, a multicentre, randomized, open-label, phase III and factorial-design trial, we assessed the relationships between renal function, demographic, and disease characteristics, including serum FLC levels, in 1595 newly diagnosed MM patients. Multivariable linear regression was utilised to identify factors that were associated with renal function at diagnosis. A receiver operating characteristic curve (ROC) was used to identify the optimal threshold for serum FLC level at diagnosis to predict severe RI. Results 52.8% of patients had an estimated glomerular filtration rate (eGFR) ≥60 ml/min/1.73 m2 (no RI), 37.3% an eGFR 30–59 ml/min/1.73 m2 (mild to moderate RI), and 9.8% an eGFR 800 mg/L as the optimal cut-off associated with severe RI (area under curve 0.86, 95% confidence interval 0.77–0.84). Conclusion There was a strong relationship between higher serum FLC levels at diagnosis and the severity of RI that was irrespective of the paraprotein type. We report an increased risk of severe RI in patients presenting with serum FLC levels above 800 mg/L at diagnosis.

Keywords

• Myeloma
• Serum free light chain level
• Renal impairment