Radiotherapy (RT) following breast conserving surgery (BCS) has been shown to reduce local recurrence, is cost-effective, and remains the standard of care for women with early-stage breast cancer who prefer breast conservation. However, more recent trials have demonstrated lower local recurrence risk with the omission of RT after BCS in older patients who are treated with tamoxifen (TAM). This study examines the cost-effectiveness of RT following BCS in older women.
Materials/Methods
Using a decision tree with embedded Markov process models, a cost-utility analysis was performed to compare strategies of RT plus TAM versus TAM alone in a hypothetical cohort of 70-year-old women following BCS until death. The base-case local recurrence risk was obtained from the updated Cancer and Leukemia Group B 9343 trial. Probabilities for local recurrence, distant metastasis with local control and local recurrence, and breast cancer mortality were obtained from the medical literature including the updated Toronto-British Columbia trial. Potential excess mortality and costs of RT-induced second malignancy were included in the base-case and those associated with heart disease were considered in the sensitivity analysis. Direct medical (2006 Average Medicare reimbursement), and nonmedical (patient time and transportation) costs and patient utilities for various health states were included. It was assumed that patients were treated using 3-dimensional conformal RT. Incremental cost-effectiveness ratios (ICER) were calculated per quality-adjusted life year (QALY) using a 3% discount rate. Sensitivity analyses were performed on key variables including patient age, recurrence risks, RT-induced toxicity risks, utilities for health states, discount rate, and costs.
Results
In the base-case analysis, the addition of RT resulted in a cost increase of $4,400 and an increase of 0.62 QALYs per patient, yielding an ICER of $7,100/QALY. Sensitivity analysis revealed the ICER to be highly sensitive to the quality-of-life benefit associated with a reduction in local relapse risk due to RT, moderately sensitive to heart disease risk, but less sensitive to age than expected. It was also relatively insensitive to plausible increases in RT costs, and second cancer risk.
Conclusions
RT following BCS in older women, including those 80 years of age, is cost-effective with an ICER well below the commonly cited threshold for cost-effective health care ($50,000-$100,000). Assessing patients' preferences for a decrease in local recurrence remains important even in older women with early stage breast cancer.
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