At a median follow-up of 5.0 years ( Interquartile Range ( IQR ) 3.4-7 .0 ) , the IBTR rate was 1.5 % ( three cases ) in the APBI group ( 95 % confidence interval ( CI ) 0.1-3 .0 ) and in the WBI group ( three cases ; 95 % CI 0.0-2 .8 ) .