The 3-year progression-free survival rate was 94.6 % ( 95 % confidence interval [ CI ] , 91.5 to 97.7 ) in the radiotherapy group and 90.8 % ( 95 % CI , 86.9 to 94.8 ) in the group that received no further therapy , with an absolute risk difference of -3.8 percentage points ( 95 % CI , -8.8 to 1.3 ) .