348pchemoresistance to Neoadjuvant Chemotherapy in Young Patients with Er-positive Breast Cancer.

Aim: The incidence of breast cancer in young women (<35 years of age) is about 9.5% in Korea and it is higher than in Western countries. Neoiadjuvant chemotherapy could be considered in young patients to avoid mastectomy. In estrogen receptor (ER)-positive breast cancer, young age is associated with poor prognosis. The possible reason several reports have suggested is the resistance to tamoxifen in adjuvant treatment. However, it is reported that adjuvant chemotherapy is less effective in ER-positive tumors than ER-negative tumors. We tried to evaluate the benefit from neoadjuvant chemotherapy and the chemoresistance in young patients with ER-positive breast cancer excluding the effect of endocrine treatment.