Correlation of levels of Akt phosphorylation at Ser473 with benefit from paclitaxel chemotherapy in NSABP B-28 patients with node-positive breast cancer

537 Background: We investigated the levels of tumor phospho-Akt(Ser473) (pAkt) and treatment outcome of patients with node-positive breast cancer after adjuvant treatment with doxorubicin/cyclophosphamide (AC) followed by four cycles of paclitaxel (PTX) (AC→PTX) compared with AC chemotherapy alone in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-28 trial. Methods: The primary tumors on B-28 tissue microarray were available from 1581 of 3060 patients enrolled. pAkt status was examined by immunohistochemistry with the antibody to pAkt(Ser473) (Cell Signaling Technology) at the National Cancer Institute. Levels of pAkt were quantitatively scored with the assistance of an Automated Digital Imaging System blinded to clinical outcome, and categorized by the staining index (intensity X % of staining /100) of > 2 (high) and ≤ 2 (low). The association between tumor pAkt level and clinical outcome at 10 years was assessed using multivariate Cox modeling adjusting for age, tumor size, number of p...