Pretransplant serum beta-2 microglobulin level is a potential novel prognostic marker of overall survival after allogeneic hematopoietic cell transplantation - a retrospective observational study

Although elevated serum beta-2 microglobulin (BMG) has been reported as a poor prognostic marker for various hematological malignancies, no study has assessed its prognostic significance in allogenec hematopoietic cell transplantation (allo-HCT). Therefore, we conducted this retrospective observational study in 227 consecutive patients with available pretransplant serum BMG levels between April 2010 and September 2017 at our institute. We also collected and retrospectively analyzed various pretransplant variables likely related to transplant outcomes. Multivariable analysis, including major prognostic variables, such as the disease risk index and the hematopoietic cell transplant-comorbidity index, showed a significant association between higher serum BMG levels and poorer overall survival (OS) in all three adjusted models [hazard ratio (HR) per its standard deviation (SD) (SD = 1.094): 1.67 (1.35-2.03; P < 0.001), HR per SD: 1.46 (1.14-1.86; P = 0.002), HR per SD: 2.03 (1.62-2.55; P < 0.001)], respectively, due to the significant association between higher serum BMG levels and relapse/progression [HR 1.52 (1.20-1.94; P < 0.001)] instead of nonrelapse mortality [HR 1.06 (0.70-1.60; P = 0.780)]. Moreover, DRI and serum BMG had statistically significantly higher c-statistic estimates for OS compared with DRI alone (c-index 0.74 and 0.68, respectively; P < 0.001). In conclusion, pretransplant serum BMG level may serve as a useful prognostic marker and help clinical decision in allo-HCT.