A population-based comparison of treatment, resource utilization, and costs by cancer stage for Ontario patients with HER2-positive breast cancer

PURPOSE: We sought to expand the currently limited, Canadian, population-based data on the characteristics, treatment pathways, and health care costs according to stage in patients with human epidermal growth factor receptor-2 positive (HER2+) breast cancer (BC). METHODS: We extracted data from the publicly funded health care system in Ontario. Baseline characteristics, treatment patterns, and health care costs were descriptively compared by cancer stage (I–III vs. IV) for adult women diagnosed with invasive HER2+ BC between 2012 and 2016. Resource use was multiplied by unit costs for publicly funded health care services to calculate costs. RESULTS: Overall, 4535 patients with stage I–III and 354 with stage IV HER2+ BC were identified. Most patients with stage I–III disease were treated with surgery (4372, 96.4%), with the majority having a lumpectomy, and 3521 (77.6%) received radiation. Neoadjuvant (NAT) and adjuvant (AT) systemic treatment rates were 20.1% (n = 920) and 88.8% (n = 3065), respectively. Systemic treatment was received by 311 patients (87.9%) with metastatic HER2+ BC, 264 of whom (84.9%) received trastuzumab. Annual health care costs per patient were nearly 3 times higher for stage IV vs. stage I–III HER2+ BC. CONCLUSION: Per-patient annual costs were substantially higher for women with metastatic HER2+ BC, despite less frequent exposure to surgery and radiation compared to those with early stage disease. Increasing NAT rates in early stage disease represent a critical opportunity to prevent recurrence and reduce the costs associated with treating metastatic HER2+ BC. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s10549-020-05976-w) contains supplementary material, which is available to authorized users.