After a median follow-up of 68 months , disease-free survival at 5 years was 91.1 % in the exemestane-ovarian suppression group and 87.3 % in the tamoxifen-ovarian suppression group ( hazard ratio for disease recurrence , second invasive cancer , or death , 0.72 ; 95 % confidence interval [ CI ] , 0.60 to 0.85 ; P < 0.001 ) .