Correlation of Serum β2-Microglobulin with Renal Function and Clinical Outcomes in Multiple Myeloma

Open Access

Abstract

Background: Renal impairment is a frequent complication in multiple myeloma (MM) and significantly affects prognosis. Serum β2-microglobulin (β2-MG) is a well-recognized biomarker of tumor burden, yet its relationship with renal function and treatment response remains incompletely characterized. Aim of the study: To evaluate the correlation of serum β2-MG with renal function and clinical outcomes in patients with MM and to determine its predictive utility for post-treatment renal recovery. Methods & Materials: In this prospective observational study, 54 adult MM patients were stratified into two groups based on baseline serum β2-MG (<3.5 mg/L and ≥3.5 mg/L). Baseline demographic, clinical, and laboratory data—including urinary protein-to-creatinine ratio (PCR), estimated glomerular filtration rate (eGFR), κ/λ free light chain (FLC) ratio, and neutrophil gelatinase-associated lipocalin (NGAL)—were collected. Patients received standard anti-myeloma therapy and were followed for six months. Correlations between β2-MG and renal/clinical biomarkers were assessed using Spearman’s correlation. Post-treatment outcomes were compared between groups, and receiver operating characteristic (ROC) analysis was performed to identify optimal β2-MG thresholds for predicting poor renal response. Result: Patients with β2-MG ≥3.5 mg/L exhibited significantly higher urinary PCR (median 1.60 vs. 0.68 g/g, p<0.001), κ/λ FLC ratio (median 2.20 vs. 1.28, p<0.001), and NGAL levels (median 1.55 vs. 1.12 pg/mL, p<0.001), along with lower eGFR (mean 45.3 vs. 65.2 mL/min, p<0.001). Post-treatment, the high β2-MG group had poorer renal recovery, with significantly lower odds of achieving urinary PCR <1.0 g/g, eGFR >60 mL/min, normalized κ/λ FLC ratio, and NGAL <1.5 pg/mL (all p<0.001). Serum β2-MG correlated strongly with urinary PCR (r=0.71), eGFR (r=–0.75), κ/λ FLC ratio (r=0.68), and NGAL (r=0.66; all p<0.001). ROC analysis identified β2-MG cut-offs of 3.75–3.95 mg/L for predicting poor renal response with high sensitivity (80–88%) and specificity (87–90%). Conclusion: Serum β2-MG is a robust biomarker reflecting both disease burden and renal impairment in MM. Elevated β2-MG levels predict poorer renal outcomes and may serve as a valuable tool for risk stratification and treatment monitoring.