Economic Evaluation of Breast Cancer Screening: A Study Based on Digital Mammography in Canada

Academic Background

Breast cancer (BC) is one of the most commonly diagnosed cancers in women and the second leading cause of cancer-related deaths in North America. Although significant progress has been made in breast cancer treatment over the past decade, leading to improved survival rates, these advances have been accompanied by rising treatment costs. These costs have surged particularly since the introduction of novel systemic therapies. Consequently, balancing improved treatment outcomes with cost containment has become a critical challenge for public health policymakers and healthcare system administrators.

Mammographic screening is an essential tool for the early detection of breast cancer, as it effectively reduces mortality and morbidity by identifying BC at earlier, more treatable stages. However, there remains ongoing debate regarding the cost-effectiveness of different screening strategies, especially as treatment costs continue to rise. Although the United States Preventive Services Task Force (USPSTF) recommended in 2024 that the starting age for breast cancer screening be lowered from 50 to 40 years, Canada’s Task Force on Preventive Health Care has not included economic analysis as a basis for its guidelines. This study aims to evaluate the cost-effectiveness of digital mammography-based breast cancer screening under contemporary Canadian treatment standards.

Paper Source

This research was authored by Anna N. Wilkinson, James G. Mainprize, Martin J. Yaffe, and other experts from various Canadian institutions, covering fields such as family medicine, physical science, pharmacy, surgery, and radiology. The study was published on January 2, 2025, in the journal JAMA Network Open under the title: Cost-Effectiveness of Breast Cancer Screening Using Digital Mammography in Canada.

Study Design and Methods

Simulation Model and Data Sources

The study employed the OncoSim-Breast microsimulation model, developed by the Canadian Partnership Against Cancer and Statistics Canada. This model simulates the natural history, progression, and detection of breast cancer for female individuals from birth to death. It enables predictions of clinical outcomes and treatment costs under varying screening strategies. The model has been validated using empirical data from the Canadian Cancer Registry and vital statistics.

The analysis used publicly-funded activity-based costing data from Ontario, Canada, for 2023. The study modeled a cohort of Canadian women born in 1975, tracking them from ages 40 to 99 under various screening strategies and corresponding treatment pathways. It assumed universal participation in digital mammographic screening, without stratification by cancer risk.

Screening Strategies

The study modeled five different screening regimens: 1. No screening: Used as the control group. 2. Biennial screening at ages 50-74 (B50-74): The current standard in Canada. 3. Biennial screening at ages 40-74 (B40-74). 4. Annual screening at ages 40-74 (A40-74). 5. Hybrid strategy (A40-49/B50-74): Annual screening for ages 40-49 and biennial screening for ages 50-74.

Key Outcomes and Cost-Effectiveness Analysis

The key outcomes analyzed were: - Deaths averted: The number of breast cancer deaths prevented due to screening. - Life-years (LYs) gained: The number of additional years of life resulting from screening. - Quality-adjusted life-years (QALYs) gained: The life-years gained, adjusted for quality of life. - Incremental Cost-Effectiveness Ratios (ICERs): The cost per death averted, cost per LY gained, and cost per QALY gained.

Sensitivity analyses were conducted to examine the impacts of participation rates, recall rates, and variations in estimated screening mortality benefits.

Results

Clinical Benefits of Screening

The findings indicated that starting screening earlier (at age 40 instead of age 50) was associated with better clinical outcomes. Specifically, earlier screening resulted in more deaths averted, more life-years saved, and more QALYs gained compared to beginning at age 50. Key results included: - B40-74 strategy: Compared to B50-74, generated savings of CAD$49,759 per death averted, CAD$1,558 per LY gained, and CAD$2,007 per QALY gained. - A40-74 strategy: Although it incurred higher screening costs, it demonstrated the best clinical outcomes, with costs of CAD$25,501 per death averted, CAD$1,100 per LY gained, and CAD$1,447 per QALY gained.

Cost-Effectiveness Analysis

From a health system perspective, the B40-74 strategy was a cost-saving public health intervention, while the A40-74 strategy represented a highly cost-effective approach for achieving optimal breast cancer outcomes. Specifically: - B40-74 strategy: Compared to B50-74, saved CAD$49,759 per death averted, CAD$1,558 per LY gained, and CAD$2,007 per QALY gained. - A40-74 strategy: Compared to B50-74, incurred costs of CAD$25,501 per death averted, CAD$1,100 per LY gained, and CAD$1,447 per QALY gained.

Sensitivity Analyses

The sensitivity analysis demonstrated that even when diagnostic recall costs were doubled, the B40-74 strategy continued to show cost savings. Additionally, reducing recall rates to the Canadian target of 5% improved the cost-effectiveness of the B40-74 strategy. For the A40-74 strategy, the results showed robust cost-effectiveness, even at moderate participation rates.

Conclusions and Implications

This study concludes that breast cancer screening costs, though higher with increased screening frequency, were entirely or substantially offset by savings in reduced treatment costs. Digital mammography is a highly cost-effective tool for significantly reducing breast cancer mortality. The findings have important policy implications for single-payer healthcare systems and advocate for increased investment in screening programs.

Study Highlights

1. Economic Benefits of Early Screening: Initiating breast cancer screening at age 40 not only prevented more deaths but also resulted in substantial healthcare savings by reducing treatment costs.
2. Comprehensive Cost Analysis: This study incorporated the latest treatment costs into the economic model, providing an updated and accurate assessment of cost-effectiveness.
3. Policy Recommendations: These findings strongly support lowering the recommended starting age for routine screening to 40 years and exploring the feasibility of annual screening for broader implementation.

Study Limitations

While this study provides important economic insights, it has some limitations. For instance, the model used an average sensitivity for mammography, which may not adequately account for variations in breast density. Additionally, societal costs (e.g., lost productivity due to treatment) and private health expenditures were not included in the analysis. Future research should investigate other screening modalities, such as tomosynthesis or MRIs, and evaluate strategies tailored to individual risk.

Summary

As the costs of breast cancer management continue to rise with advances in treatment, the cost-effectiveness of early detection through mammographic screening has also improved significantly. By using a microsimulation model, the study demonstrated that annual screening for women aged 40 to 74 years is highly cost-effective, significantly improves clinical outcomes, and reduces the healthcare system’s treatment burden. These results provide a strong evidence base for policy development, emphasizing the importance of regularly reassessing the cost-effectiveness of population-based screening programs. Early diagnosis, which reduces the cost and burden of treatment, will become ever more critical as treatment costs escalate.