Both progression-free and overall survival were significantly longer with high-dose melphalan plus stem-cell transplantation than with MPR ( median progression-free survival , 43.0 months vs. 22.4 months ; hazard ratio for progression or death , 0.44 ; 95 % confidence interval [ CI ] , 0.32 to 0.61 ; P < 0.001 ; and 4-year overall survival , 81.6 % vs. 65.3 % ; hazard ratio for death , 0.55 ; 95 % CI , 0.32 to 0.93 ; P = 0.02 ) .