Aim: to determine whether serum HER-2/neu level could be used as a prognostic factor in locally advanced breast cancer (LABC) and metastatic breast cancer (MBC). Methods: a prospective cohort study was done in LABC and MBC patients in dr. Sardjito Hospital Yogyakarta from April 2006 to March 2008. Serum concentration of HER-2/neu was measured by ELISA done before and after chemotherapy. HER-…