5 year event-free survival was 58 % ( 95 % CI 48-66 ) in patients in the trastuzumab group and 43 % ( 34-52 ) in those in the chemotherapy group ; the unadjusted hazard ratio ( HR ) for event-free survival between the two randomised HER2-positive treatment groups was 0.64 ( 95 % CI 0.44-0 .93 ; two-sided log-rank p = 0.016 ) .