Abstract
INTRODUCTION: The benefit of adjuvant trastuzumab with chemotherapy is well established for women with higher risk human epidermal growth factor receptor 2-positive (HER2(+)) breast cancer. However, its role in older patients with smaller, node-negative tumors is less clear. We conducted a retrospective, sequential cohort study of this population to describe the impact of trastuzumab on breast cancer outcomes and cardiac safety. PATIENTS AND METHODS: Women ≥ 55 years with ≤ 2 cm, node-negative, HER2(+) breast cancer were identified and electronic medical records reviewed. A no-trastuzumab cohort of 116 women diagnosed between January 1, 1999 and May 14, 2004 and a trastuzumab cohort of 128 women diagnosed between May 16, 2006 and December 31, 2010 were identified. Overall survival and distant relapse-free survival were estimated by Kaplan-Meier methods. RESULTS: The median ages of the trastuzumab and no-trastuzumab cohorts were 62 and 64 years, respectively. More patients in the trastuzumab cohort had grade III (P = .001), lymphovascular invasion (P = .001), or estrogen receptor-negative (P < .001) cancers. The majority of the trastuzumab cohort received chemotherapy versus one-half of the no-trastuzumab cohort (98% vs. 53%; P < .0001). The median follow-up was 4 versus 9 years in the trastuzumab versus no-trastuzumab cohorts; therefore, outcomes at 4 years are reported. Despite the higher-risk tumor features in the trastuzumab group, the 4-year overall survival was 99% in both cohorts; the distant relapse-free survival was 99% versus 97% in the trastuzumab versus no-trastuzumab cohorts. Four (3.1%; 95% confidence interval, 1.0%-7.8%) women in the trastuzumab cohort and 1 in the no-trastuzumab cohort developed symptomatic heart failure. There were no cardiac-related deaths in either arm. CONCLUSION: Following adjuvant trastuzumab with chemotherapy, selected older women with small, node-negative, HER2(+) breast cancers have excellent disease control. The rate of cardiac events is low.