ERBB2 and breast neoplasm: No formal subgroup analyses were done because of the low number of primary endpoint events, but frequencies of ipsilateral breast tumour relapse, regional relapse, and distant relapse were tabulated according to age, grade, and ER and HER2 status for descriptive purposes; as expected, ipsilateral breast tumour relapse occurred in more of the patients with higher-grade primary tumours (appendix p 7).