PURPOSE: To present a decision model that describes the clinical and economic outcomes of node-positive breast cancer with and without postmastectomy radiation therapy (PMRT). METHODS: A Markov process was constructed to project the natural history of breast cancer following mastectomy in premenopausal node-positive women. Biannual hazards of local and distant recurrence without PMRT were derived from a large meta-analysis of adjuvant systemic therapy trials for breast cancer. The addition of PMRT reduced the risk of disease relapse by an odds ratio of 0.69. Costs of PMRT ($11,600) and recurrent breast cancer ($4,250 to 16,200/year) were estimated from available literature. The model projected number of recurrences, relapse-free and overall survival, and costs to 15 years, using a discount rate of 3%. Cost-effectiveness ratios were calculated per incremental year of life and quality-adjusted year of life gained. One- and two-way sensitivity analyses were performed to determine the sensitivity of results to clinical and economic assumptions. RESULTS: The model projected 15-year relapse-free survival of 52% and 43% with and without PMRT, respectively. Overall survival was increased from 48% to 55% with PMRT, resulting in an incremental 0.29 years of life gained per subject. PMRT increased 15-year costs from $40,800 to $48,100. Cost per year of life gained was $24,900, or $22,600 when survival was adjusted for quality of life. Results of the model were relatively sensitive to radiation therapy cost and breast cancer relapse risk. CONCLUSION: This analysis suggests that PMRT offers substantial clinical benefits achieved in a cost-effective manner, with an average cost per year of life gained of $24,900. Results of the model were robust under a wide range of clinical and economic parameters.
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