Patient Characteristics
Median (range) follow-up of all 191 enrolled patients was 42 (4 to 92) months (Table 1). Baseline characteristics did not differ significantly between the rhEPO and transfusion groups. 48% patients were loss to follow up in our study.
Hemoglobin Concentrations
Baseline hemoglobin concentrations did not differ significantly between the rhEPO and the transfusion groups (Table 2). However, mean hemoglobin concentrations were significantly higher in of the rhEPO group than blood transfusion group after 3 months (112.65 vs. 86.10 g/L) and 6 months (128.96 vs 91.41 g/L) treatment (Table 2).
Furthermore, subgroup analysis revealed that mean (SD) hemoglobin concentrations were significantly higher in the high-dose group than in low-dose group at 3 months (40.81 vs. 32.62 g/L) and at 6 months (56.98 vs. 49.16 g/L, respectively; Table 3).
Effective Treatment
The percentage of effective treatment (a very good complete response or better) was significantly higher in the rhEPO group (49%) than in the transfusion group (36%;Table 2). Subgroup analysis in rhEPO group indicated the dose of rhEPO had no influence on response evaluation (P>0.05).
Overall and Progression-Free Survival
The Kaplan-Meier estimate of overall survival for all patients was 74% at 36 months and 52% at 60 months. Estimated progression-free survival rates for all patients were 52% at 36 months and 43% at 60months (Figure 1).
Estimated overall survival rates were 82% at 36 months and 68% at 60 months in the rhEPO group and 69% at 36 months and 36% at 60 months for the transfusion group. The estimated progression free survival rates were 52% at 36 months and 31% at 60 months for the rhEPO group, and 33% at 36 months and 21% at 60 months in the transplant group. In conclusion, The rhEPO group had significantly longer progression-free and overall survival than did the transfusion group (Figure 1).
Subgroup analysis revealed that the dose of rhEPO was not associated with longer OS and PFS (Figure 2).
Predictors of Progression-free and Overall Survival
Univariate analysis identified 5 risk predictors for overall survival (cancer stage III, more than 30% of bone marrow clonal plasma cell, β2-MG >3.5 mg/L, a very good partial response or better, and rhEPO; Table 3). Multivariate analysis indicated that rhEPO treatment was significantly associated with improved overall survival (hazards ratio [HR], 0.44) and progression-free survival (HR, 0.61) after adjusting for cancer stage, bone marrow clonal plasma cells, serum creatinine, β2-MG, and response to treatment.
Otherwise, progression-free survival and overall survival were significantly and inversely correlated with more than 30% BM clonal plasma cells (HR, 1.74 and 1.62, respectively) and more than 3.5 mg/L of β2-MG (HR, 1.97 and 1.82) and was positively correlated with a very good partial response or better (HR, 0.50 and HR 0.60; Table 3).