Updated breast cancer costs for women by disease stage and phase of care using population-based databases.

Background: This study assessed health care system costs and resource utilization for adult women with breast cancer in Ontario, Canada. The goal was to update costs by stage, age, and phase of care from a health care system perspective.

Data and methods: A retrospective analysis was conducted using linked population-based administrative data. The study included women diagnosed with breast cancer from 2017 to 2021, with follow-up data until 2022. Cases were matched with controls in a 1:5 ratio using birth year, local health integrative network, income quintile, and resource utilization band at baseline. Incremental costs were estimated using linear regression. The modified income quintile was the neighbourhood- or area-level income quintile.

Results: Among the 37,133 cases matched with 185,665 controls, the average age at diagnosis was 62 years. For the entire study duration, cases incurred an additional cost of $27,485 per year, compared with controls. Costs rose with disease severity, ranging from $15,588 for stage I to $137,319 for stage IV. The highest incremental costs occurred during the first 12 months after diagnosis (initial: $43,408), followed by the last 12 months before death (terminal: $25,940), and then interim years (continuous: $9,533 per year). Additionally, the incremental cost of breast cancer was higher when diagnosis was before age 70 ($28,415), compared with diagnosis at age 70 and older ($25,254).

Interpretation: The findings align with previous studies on breast cancer costs for the health care system. Additionally, variations in costs based on disease severity, care phase, and age were emphasized, highlighting higher costs for metastatic breast cancer cases, women younger than 70 years, and the initial 12 months following diagnosis.