Safety and efficacy of single-agent adjuvant trastzumab in older women with breast cancer.

Abstract

TPS109 Background: Trastuzumab is a humanized monoclonal antibody targeting the extracellular domain of the human epidermal growth factor receptor 2 (HER2) protein. The addition of trastuzumab to adjuvant chemotherapy, either concomitant or sequential, leads to better outcomes for women with HER2-positive breast cancer and in the setting of metastatic disease, single agent trastuzumab is effective and extremely well tolerated. The main adverse effect of trastuzumab is cardiotoxicity, which necessitated discontinuation prior to the planned one year of therapy in 17% of women on adjuvant trials. Since age is a risk factor for the cardiotoxicity of trastuzumab, and women ≥ 65 years were under-represented in trastuzumab clinical trials, determination of the safety and efficacy of trastuzumab in this patient population is lacking. This study is designed to define the risk-benefit profile of adjuvant single-agent trastuzumab in older women. Methods: This open label, single arm, multi-center, phase II study will include 124 women with stage I-III, HER2+ (defined as either 3+ by immunohistochemistry or gene amplified by fluorescent in situ hybridization), breast cancer who undergo primary surgery (mastectomy or lumpectomy) with at least a sentinel lymph node dissection, and are unwilling to undergo or are unable to tolerate adjuvant chemotherapy. Trastuzumab will be given, at 8mg/kg IV loading dose followed by 6mg/kg IV every three weeks, for 52 weeks. Patients will be followed prospectively for five years or until death, whichever comes first. The primary objective of the study is to evaluate the three-year cumulative incidence of cardiac events. Secondary objectives include i) the three-year cumulative incidence of asymptomatic decline in Left Ventricular Ejection Fraction; ii) the five-year cumulative incidence of cardiac events; iii) three-year disease-free and overall survival; iv) identification of correlative biomarkers of cardiac events (troponin-I, N-terminal brain natriuretic protein, and pro-inflammatory cytokines); and v) the longitudinal changes in Health-related Quality of Life, functional, cognitive, and mental status. Ten patients have been enrolled thus far.