Partial-Breast Irradiation Versus Whole-Breast Irradiation for Early-Stage Breast Cancer: A Decision Analysis

Abstract

Purpose—To compare the quality-adjusted life expectancy (QALE) between women treated with whole-breast radiation therapy (WBRT) and partial-breast irradiation (PBI) for estrogen-receptor (ER)-positive early-stage breast cancer. Methods and materials—We developed a Markov model to describe health states in the 15 years following radiotherapy (RT) for ER-positive early-stage breast cancer. Breast recurrences were separated into local recurrences (LR) and elsewhere failures (EF). Ipsilateral breast tumor recurrence (IBTR) risk was extracted from the Oxford overview, and rates and utilities were adapted from the literature. We studied two cohorts of women (aged 40 years and aged 55 years), both of whom received adjuvant tamoxifen. Results—Assuming a NED-PBI (no evidence of disease) utility of 0.93, QALE after PBI (and WBRT) was 12.61 (12.57) and 12.10 (12.06) years for 40-year-old and 55-year-old women, respectively. The NED-PBI utility thresholds for preferring PBI over WBRT were 0.923 and 0.921 for 40-year-old and 55-year-old women, respectively, both slightly greater than the NED-WBRT utility. Outcomes were sensitive to the utility of NED-PBI, the PBI hazard ratio (HR) for local recurrence, the baseline IBTR risk, and the percentage of IBTRs that were local. Overall, the degree of superiority of PBI over WBRT was greater for 55-year-old women than for 40-year-old women. Conclusions—For most utility values of the NED-PBI health state, PBI was the preferred treatment modality. This result was highly sensitive to patient preferences and was also dependent upon patient age, PBI efficacy, IBTR risk, and the fraction of IBTRs that were local.