Abstract
PurposeThe NSABP Trial B-31 and NCCTG Trial N9831 (B-31/N9831 trials, Romond et al. in N Engl J Med 353:1673–84, 2005. doi:10.1056/NEJMoa052122; Perez et al. in J Clin Oncol 32:3744–52, 2014. doi:10.1200/JCO.2014.55.5730) established the efficacy of adjuvant trastuzumab for patients with HER2-positive early stage breast cancer. We aimed to estimate the overall survival (OS) and relapse-free survival (RFS) of HER2-positive non-metastatic breast cancer patients treated with adjuvant trastuzumab in a clinical practice setting in the United States.MethodsAdult women initiating adjuvant trastuzumab within 1 year of breast cancer surgery were identified in the health claims database of the US Department of Defense (01/2003–12/2012). OS and RFS unadjusted rates at 4 and 6 years after the first trastuzumab treatment following the breast cancer diagnosis were estimated from Kaplan–Meier analyses.ResultsThe study sample included 3188 women followed for a median of 3.3 years after trastuzumab initiation and treated continuously with trastuzumab for a median of 12 months. The OS rates (95 % confidence intervals) at 4 and 6 years were 90.0 % (88.6–91.2) and 87.1 (85.3–88.6), respectively. The corresponding RFS rates were 75.8 % (74.0–77.5) and 72.7 (70.7–74.7), respectively. The OS and RFS rates at 6 years reported in the B-31/N9831 trials were 89.8 and 81.4 %, respectively.ConclusionsOS rates estimated in this study were in range with those estimated in the B-31/N9831 trials, while RFS rates were lower. However, patients in the B-31/N9831 trials were younger and possibly had fewer comorbidities than patients in the current study; these differences were not adjusted for in the crude OS and RFS analyses.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-2008-9) contains supplementary material, which is available to authorized users.
Highlights
Most patients with breast cancer in developed countries are diagnosed in the early stages of disease (National Cancer Institute 2014; Sant et al 2003; Allemani et al 2013; Walters et al 2013) and undergo tumor-removing surgery, followed by adjuvant chemotherapy and/or targeted therapies against specific overexpressed receptors
The overall survival (OS) and relapse-free survival (RFS) rates at 6 years reported in the B-31/N9831 trials were 89.8 and 81.4 %, respectively
OS rates estimated in this study were in range with those estimated in the B-31/N9831 trials, while RFS rates were lower
Summary
The effectiveness of trastuzumab as adjuvant treatment for HER2-positive breast cancer has been studied in observational studies (Zurawska et al 2013; Webster et al 2012; Peterson et al 2014; Palmieri et al 2011; Jensen et al 2012; Inwald et al 2014; Hayashi et al 2013; Bonifazi et al 2014; Vici et al 2014). To our knowledge, only one of these observational studies was US-based (Hayashi et al 2013)
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