Real World Evidence Study to Assess Incidence, Treatment Patterns, Clinical Outcomes, and Health Care Resource Utilization in Early-Stage, High-Risk HER2-Negative Breast Cancer in Alberta, Canada.

Abstract

Background: Data are needed to improve the current understanding of the epidemiology of patients with high-risk, HER2-negative, early breast cancer (eBC) (hormone receptor positive [HR+]/HER2-negative BC and triple-negative BC [TNBC]).

Patients and methods: This retrospective longitudinal cohort study used real-world, population-level data that included all individuals newly diagnosed with high-risk, HER2-negative eBC in Alberta, Canada, between 2010 and 2019. Data on treatment, laboratory results and pathology findings were collected through electronic health records and administrative databases.

Results: The annual cumulative incidence of high-risk, HER2-negative eBC ranged from 6% to 9% of all incident BC cases. Individuals with TNBC were more likely to be younger, had stage II disease, grade 3 histology and received systemic therapy at a community centre (P < .05) compared to individuals with HR+/HER2-negative eBC. Only 14% of individuals diagnosed in 2010-2017 underwent germline BRCA testing postdiagnosis. Neoadjuvant systemic therapy was given to 37% of individuals. Adjuvant systemic therapy use increased from 77% (2012-2015) to 84% (2019). The 5-year overall survival (OS) from initiation of adjuvant systemic therapy or date of surgery (for individuals who did not receive adjuvant systemic therapy) was 77% (95% CI: 75-79). OS was significantly worse among individuals who were older, had grade 3 histology, had stage III disease, or had nodal involvement (P < .05). OS among individuals with TNBC between 2016 and 2019 who initiated adjuvant capecitabine was markedly worse compared to the overall cohort (2-year OS: 70% vs. 89%).

Conclusion: Outcomes analyses in this high-risk, HER2-negative eBC population suggest a continued unmet clinical need.