Effect of Delay in Initiation of Adjuvant Trastuzumab and Dose Interruptions on Overall Treatment Outcome in Breast Cancer Patients, a Retrospective Study

Abstract

ER2 amplification or protein over-expression is found in 20% of invasive breast cancers. It’s clearly associated with accelerated cell growth and proliferation and poor clinical outcome. The amplification of HER2 was historically an adverse prognostic factor associated with a higher risk of recurrence, lack of or lower levels of ER expression, and relative resistance to endocrine therapy and CMF based chemotherapy. In November 2006, the FDA approved Trastuzumab as adjuvant therapy for HER2-positive breast cancer. Using a variety of different adjuvant chemotherapy regimens and employing Trastuzumab in different schedules and sequences, they all showed significant improvements in DFS (reduction in risk of 50% on average) and OS. Subset analyses demonstrated comparable RR reduction regardless of tumor size, nodal status, or hormone receptor status, resulting in the rapid incorporation of Trastuzumab into standard treatment recommendations for women with HER2+ breast cancer. We aimed in this study to assess the impact of delaying the initiation of adjuvant Trastuzumab for more than three months after the diagnosis of breast cancer and the effect of irregular and interrupted doses of adjuvant Trastuzumab, on progression free Survival, relapse, and overall survival (OS) among patients with breast cancer.