118P Real-world treatment patterns and clinical outcomes among high risk, early stage HER2-negative breast cancer (BC) patients in Alberta, Canada

Abstract

Data are needed to improve the current understanding of the epidemiology and clinical management of high-risk early stage HER2- BC patients. This study was a retrospective longitudinal cohort study using real-world, population-level data from Alberta, Canada. All individuals newly diagnosed with high-risk, stage II/III HER2- BC in Alberta, Canada between 2013-2019 were included. Data on treatment, laboratory results and pathology findings were collected through electronic health records and administrative databases. High-risk BC was defined as receipt of adjuvant systemic therapy within 120 days of surgery as well as the presence of the following characteristics: 1) For triple-negative BC (TNBC): tumor 2+ cm (AJCC T2 or greater) or axillary lymph node (LN) involvement; 2) For hormone-receptor positive (HR+/HER2-): four or more positive LNs. Treatment eras were separated into pre/post 2016. Overall survival (OS) was defined as the date of diagnosis to death from any cause or last known contact. The annual cumulative incidence of early-stage, high-risk, HER2- BC ranged from 6% to 9%. Individuals with TNBC were more likely to be younger, have grade 3 histology, stage II BC, and receive systemic therapy at a community centre (p < 0.05) when compared with HR+/HER2- BC. Germline BRCA testing was not widely conducted in this patient population, with an estimated 14% of patients diagnosed in 2010-2017 being tested at some point post-diagnosis. Neoadjuvant systemic therapy was given to 37% of patients with high-risk BC. The 5-year OS from initiation of adjuvant systemic therapy (for patients who received adjuvant systemic therapy) or date of surgery (for patients who did not receive adjuvant systemic therapy) was 77% (95% CI: 75 to 79). OS was significantly worse among patients who were older, had grade 3 histology, stage III BC, or had LN involvement (p < 0.05). OS among patients with TNBC between 2016-2019 who initiated adjuvant capecitabine was markedly worse than that of the overall cohort (2-year OS: 70% vs. 89%). Outcomes analyses in this population suggest a continued unmet clinical need. Additional analyses into the indications for use of systemic therapies are underway.