The rate of disease-free survival was 72.1 % in the nodal-irradiation group and 69.1 % in the control group ( hazard ratio for disease progression or death , 0.89 ; 95 % CI , 0.80 to 1.00 ; P = 0.04 ) , the rate of distant disease-free survival was 78.0 % versus 75.0 % ( hazard ratio , 0.86 ; 95 % CI , 0.76 to 0.98 ; P = 0.02 ) , and breast-cancer mortality was 12.5 % versus 14.4 % ( hazard ratio , 0.82 ; 95 % CI , 0.70 to 0.97 ; P = 0.02 ) .