In the confirmation set , the predefined cut points for this model classified patients into three subsets with differential benefit from trastuzumab with hazard ratios of 1.58 ( 95 % confidence interval [ CI ] = 0.67 to 3.69 ; P = .29 ; n = 100 ) , 0.60 ( 95 % CI = 0.41 to 0.89 ; P = .01 ; n = 449 ) , and 0.28 ( 95 % CI = 0.20 to 0.41 ; P < .001 ; n = 442 ; P ( interaction ) between the model and trastuzumab < .001 ) .