OBJECTIVES: To evaluate the cost-effectiveness of adjuvant tamoxifen + radiation therapy (tam+RT) versus tamoxifen alone in women aged 65+ undergoing breast-conserving surgery (BCS) for early-stage estrogen receptor-positive (ER+) breast cancer.

METHODS: A 5-year decision analytic/Markov model was constructed utilizing outcomes from CALGB 9343, a randomized trial comparing outcomes on tam+RT to tamoxifen alone in 636 women aged 70 and older with ER+ clinical stage I breast cancer, as well as a separate cohort of 888 women aged 65 and older with ER+ T1 breast cancer treated with BCS at Memorial Sloan Kettering from 2010-2015. Disease state transition probabilities were derived from these cohorts and several other studies evaluating clinical outcomes in breast cancer patients who underwent curative surgery for locoregional or distant recurrence with or without adjuvant RT. Costs were assessed in 2021 US dollars, and informed by the Centers for Medicare & Medicaid Services and various economic studies on average Medicare spending for RT, curative surgical procedures, and cumulative costs for treating locoregional and distant recurrence. Effectiveness was measured in quality-adjusted life-years (QALYs) using 5-year survival rates from the American Cancer Society and 15D health-related quality of life (HRQoL) scores from patient-reported outcomes assessments of breast cancer patients and survivors. The cost-effectiveness of tam+RT was assessed by the derived incremental cost-effectiveness ratio (ICER).

RESULTS: In our base-case analysis, total costs for tam+RT were $19,499, compared to $11,040 for tamoxifen alone. Total QALYs for tam+RT were 4.01, compared to 3.99 for tamoxifen alone, yielding a base-case ICER of $301,540/QALY. Probabilistic sensitivity analysis indicated that tam+RT had a 10.1% probability of being cost-effective at a willingness-to-pay (WTP) threshold of $100,000 per QALY.

CONCLUSIONS: Despite the common utilization of tam+RT as an adjuvant therapy following BCS, our model highlights serious concerns regarding its cost-effectiveness versus tamoxifen alone in older adult women with ER+ T1 breast cancer.