Serum B‐Cell Maturation Antigen as a Biomarker for Predicting Outcomes and Monitoring Patients With Waldenström Macroglobulinemia

Waldenström macroglobulinemia (WM) is an uncommon indolent B‐cell lymphoma driven by MYD88 and CXCR4 mutations. Although serum B‐cell maturation antigen (sBCMA) has been shown to be a prognostic and monitoring tool for multiple myeloma patients, it has not been evaluated among those with WM. We assessed sBCMA levels among 50 WM patients: 16 had received prior therapy, while 34 were treatment‐naïve (TN), 19 of whom never went on to require therapy (smoldering [S]WM). Levels were higher among WM patients (median, 63.76 ng/mL) than healthy subjects (median, 35.24 ng/mL; p < 0.0001). TNWM patients who required therapy showed higher initial levels (median, 137.71 ng/mL) than those with SWM (median, 50.19 ng/mL; p = 0.0002). sBCMA also correlated with disease status: levels decreased at best response (≥ minimal response; median, 38.36 ng/mL) compared to baseline (median, 117.00 ng/mL; p = 0.0078) and increased among patients who developed progressive disease (median, 79.42 ng/mL; p = 0.0625). Baseline sBCMA levels positively correlated with β2 microglobulin ( p = 0.0193) and M‐protein ( p = 0.0450), and negatively with hemoglobin ( p = 0.0090) and albumin ( p = 0.0016). Overall, these findings suggest sBCMA may serve as a biomarker for prognosis and monitoring for WM patients.