Serum BCMA levels to predict outcomes for patients with MGUS and smoldering multiple myeloma (SMM).

Abstract

8020 Background: BCMA (B-cell maturation antigen) is a TNF receptor family member found on normal and malignant B-cells, including multiple myeloma (MM). It plays a role in proliferation and antiapoptotic pathways. Levels of serum (s)BMCA are elevated in patients (pts) with plasma cell disorders (PCD) and increase with each stage of disease: healthy donor< MGUS<SMM< active untreated MM. The purpose of this study was to test whether sBCMA levels predict progression of MGUS or SMM to MM. Methods: There were 3 cohorts in this retrospective study: MGUS progressing to MM (n=42); MGUS not progressing to MM (n=49); SMM progressing to MM (n=32). sBCMA levels were measured using an ELISA-based assay with a polyclonal anti-BCMA antibody from R&D Systems (Minneapolis, MN). The Kruskal-Wallis analysis was used to assess differences. The relationships between sBCMA and both time to progression and overall survival were also assessed using Cox proportional hazard models. Results: The highest values of sBCMA were seen among pts with more advanced PCD (Table). The lowest baseline levels were seen in pts with MGUS who did not progress; the change of sBCMA over time was lowest in the MGUS non-progressors. ROC analysis identified a cutoff of 74.4 ng/mL to be predictive of progression at 5 years. This cut-point was associated with a risk ratio of progression of 5.8 (95%CI 3.2, 11.3) for all comers, a risk ratio of death for all comers of 2.5 (95%CI 1.5, 4.2), and a risk ratio of death for MGUS pts of 3.3 (95%CI 1.9, 5.7). Conclusions: Serum BCMA levels were predictive of diagnosis, progression and death among pts with MGUS or SMM. Limitations of the current study are that only a minority of pts had baseline bone marrow exams or serum FLCs to place sBCMA risk in the context of other previously described risk factors. Serum FLC is now being determined on all patients. [Table: see text]