Background: Evaluation of the long-term benefit of biologically-based regimens of trastuzumab in the early breast cancer population, and optimization of trastuzumab integration to maximize efficacy and minimize cardiac toxicity.Material and Methods: We randomized HER2-positive (FISH+) breast cancer patients with axillary lymph node positive or high risk negative, to either standard AC (60/600 mg/m2 q3wk x4) followed by T (100 mg/m2 q3wk x 4) or two trastuzumab-containing regimens; AC followed by T with trastuzumab x 1 year or TCarbo (75 mg/m2/AUC6 q3wk x 6) with trastuzumab x 1 year. Patients were prospectively stratified by number of positive nodes (0, 1-3 vs 4+) and hormone receptor status. Patients with ER and/or PR positive (HR+) tumors received hormone-directed therapy for 5 yrs after chemotherapy. The primary endpoint was disease-free survival (DFS) with 80% power (0.05 significance level) to detect an absolute difference of 7%. Secondary endpoints include overall survival (OS) and safety, including cardiac toxicity (symptomatic events and asymptomatic LVEF decline). The first two protocol-specified analyses for this study were performed at 300 and 450 disease-related events. We now report the results of the third protocol-specified analysis conducted after 650 events, expected by end of June 2009.Results: A total of 3222 patients (1072 in AC-T, 1076 in AC-TH and 1074 in TCH) were recruited between April 2001 and March 2004. Baseline characteristics of the study population will be included. Cox analysis of DFS and OS (unadjusted and adjusted for nodal status) and cardiac toxicity data will be presented for the three treatment arms.Discussion: The results of this trial help define the role of trastuzumab in the breast cancer HER2-positive adjuvant setting, as well as the risks/benefits of adjuvant trastuzumab within the context of overall safety including cardiac toxicity. This latter objective is of particular importance given that many of these women may be cured of their disease in the adjuvant setting. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 62.

The production of exosomes by tumor cells has been implicated in tumor-associated immune suppression. In this study, we show that, in mice, exosomes produced by TS/A murine mammary tumor cells target CD11b+ myeloid precursors in the bone marrow (BM) in vivo, and that this is associated with an accumulation of myeloid precursors in the spleen. Moreover, we demonstrate that TS/A exosomes block the differentiation of murine myeloid precursor cells into dendritic cells (DC) in vitro. Addition of tumor exosomes at day 0 led to a significant block of differentiation into DC, whereas addition at later time points was less effective. Similarly, exosomes produced by human breast tumor cells inhibited the differentiation of human monocytes in vitro. The levels of IL-6 and phosphorylated Stat3 were elevated 12 h after the tumor exosome stimulation of murine myeloid precursors, and tumor exosomes were less effective in inhibiting differentiation of BM cells isolated from IL-6 knockout mice. Addition of a rIL-6 to the IL-6 knockout BM cell culture restored the tumor exosome-mediated inhibition of DC differentiation. These data suggest that tumor exosome-mediated induction of IL-6 plays a role in blocking BM DC differentiation.

AT significantly improves TTP and ORR compared with AC in patients with MBC, but there is no difference in OS. AT represents a valid option for the treatment of MBC.