Prognostic significance of serum beta-2 microglobulin in patients with diffuse large B-cell lymphoma in the rituximab era

The prognostic value of serum beta-2 microglobulin for diffuse large B-cell lymphoma (DLBCL) is not well known in the rituximab era. A retrospective registry data analysis of 833 patients with de novo DLBCL treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) was conducted to establish the prognostic significance of serum beta-2 microglobulin at a ≥ 2.5 mg/L cutoff. Five-year progression-free survival (PFS, 76.1% vs. 41.0%; p < 0.001) and overall survival (OS, 83.8% vs. 49.2%; p < 0.001) were significantly worse in patients with elevated serum beta-2 microglobulin (n = 290, 34.8%). Furthermore, the five parameters of the International Prognostic Index, accompanying B symptoms, bone marrow involvement and impaired renal function were associated with worse PFS and OS. In multivariate analysis, elevated beta-2 microglobulin was a significant poor prognostic factor for PFS (hazard ratio [HR], 1.70; 95% confidence interval [CI], 1.29-2.24; p < 0.001) and OS (HR, 2.0; 95% CI, 1.47-2.75; p < 0.001). In an independent validation cohort of 258 R-CHOP treated patients with de novo DLBCL, elevated beta-2 microglobulin levels remained a significant poor prognostic factor for PFS (HR, 2.03; 95% CI, 1.23-3.32; p = 0.005) and exhibited a strong trend of association with worse OS (HR, 1.64; 95% CI, 0.98-2.75; p = 0.062). The significance of serum beta-2 microglobulin levels as an independent prognostic factor for patients with DLBCL receiving R-CHOP is confirmed.