Role of ErbB2 in selection for adjuvant tamoxifen or aromatase inhibitors

This study analysed data after a median of 51 months follow-up from 4922 postmenopausal women with early hormone-sensitive breast cancer randomly assigned to 5 years of treatment with letrozole or tamoxifen. Tumors from 3650 (74%) patients were centrally assessed for estrogen receptor, progesterone receptor and ErbB2 status. By central assessment, 7% (257 of 3650) of tumors were classified as ErbB2-positive. Disease-free survival was significantly worse in patients with ErbB2-positive tumors (p < 0.0001). Letrozole improved disease-free survival compared with tamoxifen regardless of ErbB2 status.