Outcomes of women with early-stage breast cancer receiving adjuvant trastuzumab

Introduction Large randomized trials assessing the benefit of adjuvant trastuzumab in early-stage breast cancer positive for the human epidermal growth factor receptor 2 (HER2) have demonstrated a significant improvement in survival. The objective of the present study was to describe the outcomes of women who received adjuvant trastuzumab for HER2-positive breast cancer in British Columbia since publicly funded population-based use was initiated in July 2005. Methods Women from British Columbia, newly diagnosed with stage I-III breast cancer between July 2004 and December 2006, who were positive for HER2 overexpression by immunohistochemistry (3+) or amplification by fluorescence in situ hybridization (ratio >= 2.0) were included in the study. Data were collected from the prospectively assembled BC Cancer Agency Outcomes Unit, with cases linked to the provincial pharmacy data repository to determine the proportion of women who received adjuvant trastuzumab. Results Our retrospective study identified 703 HER2-positive patients, of whom 480 (68%) received trastuzumab. In patients receiving trastuzumab, the 2-year relapse-free survival was 96.1% [95% confidence interval (CI): 93.6% to 97.7%] and the overall survival was 99.3% (95% Cl: 97.9% to 99.8%). Among node-negative and -positive patients, the 2-year relapse-free survival was 97.8% and 94.8% respectively (p = 0.09) for the trastuzumab-treated group and 90.9% and 77.3% (p = 0.01) for the group not receiving trastuzumab (n = 223). Site of first distant metastasis was the central nervous system in 19.5% of the entire cohort and in 37.5% of patients treated with trastuzumab. Discussion This population-based analysis of adjuvant trastuzumab use among Canadian women demonstrates highly favorable outcomes at the 2-year follow-up.