Initiation of adjuvant chemotherapy and trastuzumab for human epidermal growth receptor 2-positive early invasive breast cancer in a population-based cohort study of older women in England.

BACKGROUND: Clinical guidance on recommended treatment for older patients with breast cancer is often ambiguous, particularly in the context of comorbidities and poor functional status. Older patients, aged 70 years and over, account for a substantial proportion of women with breast cancer yet are underrepresented in randomized controlled trials. This paper investigates the initiation of adjuvant chemotherapy and trastuzumab in older patients in routine care. MATERIALS AND METHODS: Women, aged 50 years and over, newly diagnosed with human epidermal growth receptor 2 (HER2)-positive early invasive breast cancer from January 2014 to December 2017 were identified from the England Cancer Registry. Chemotherapy and trastuzumab use was obtained from the Systemic Anti-Cancer Therapy (SACT) dataset. Patient and tumor characteristics influential in treatment decision-making were included in multilevel mixed-effects logistic regression models. RESULTS: 10% of women had HER2-positive tumors. Initiation of adjuvant chemotherapy and trastuzumab decreased with age from ≥70% among women aged 50-64 years to