Factors influencing HER2 discordance in nonmetastatic breast cancer and the role of neoadjuvant therapy.

The rates of and the factors influencing HER2 discordance in patients receiving neoadjuvant therapy for breast cancer are investigated. This study retrospectively examines the rates of HER2 and hormone receptor discordance between the biopsy and postoperative resection specimens of 400 female early-stage breast cancer patients. 133 (33.3%) patients had received neoadjuvant therapy. The rate of HER2 discordance between biopsy and resection specimens was 1.7% in the control group and 5.3% in the neoadjuvant therapy group (p = 0.018). The rate of HER2 discordance was higher in younger patients and in patients with T1 tumors in the neoadjuvant therapy group. Neoadjuvant therapy, age <40 years and smaller tumor size were independent risk factors for HER2 discordance.