Gene expression profiling of primary HER2-positive breast cancers treated with neoadjuvant trastuzumab

Trastuzumab, a humanized monoclonal antibody directed to the HER2 protein, is the standard-of-care treatment for patients with HER2 positive breast cancer, reducing the risk of relapse and death in patients. Nonetheless, some patients do not benefit from this treatment, underscoring the need to identify patients for whom chemotherapy + trastuzumab is adequate versus patients requiring additional drugs. The series comprised 18 incisional biopsies of breast carcinomas derived from patients that received neoadjuvant trastuzumab based therapy. Gene expression profiling was performed using RNA from formalin-fixed paraffin-embedded tissues core biopsies from 18 patients with primary HER2-positive breast cancer before treatment with neoadjuvant chemotherapy and trastuzumab.