Physician trajectories of abandoning long-course breast radiotherapy and their cost impact

To examine variation in trajectories of abandoning conventionally fractionated whole-breast irradiation (CF-WBI) for adjuvant breast radiotherapy among physician peer groups and the associated cost implications.

Medicare claims data were obtained from the Chronic Conditions Data Warehouse for fee-for-service beneficiaries with breast cancer in 2011-2014.

We used social network methods to identify peer groups of physicians that shared patients. For each physician peer group in each time period (T1 = 2011-2012 and T2 = 2013-2014), we calculated a risk-adjusted rate of CF-WBI use among eligible women, after adjusting for patient clinical characteristics. We applied a latent class growth analysis to these risk-adjusted rates to identify distinct trajectories of CF-WBI use among physician peer groups. We further estimated potential savings to the Medicare program by accelerating abandonment of CF-WBI in T2 using a simulation model.

Use of conventionally fractionated whole-breast irradiation was determined from Medicare claims among women ≥ 66 years of age who underwent adjuvant radiotherapy after breast conserving surgery.

Among 215 physician peer groups caring for 16 988 patients, there were four distinct trajectories of abandoning CF-WBI: (a) persistent high use (mean risk-adjusted utilization rate: T1 = 94.3%, T2 = 90.6%); (b) decreased high use (T1 = 81.3%, T2 = 65.3%); (c) decreased medium use (T1 = 60.1%, T2 = 44.0%); and (d) decreased low use (T1 = 31.6%, T2 = 23.6%). Peer groups with a smaller proportion of patients treated at free-standing radiation facilities and a larger proportion of physicians that were surgeons tended to follow trajectories with lower use of CF-WBI. If all physician peer groups had practice patterns in T2 similar to those in the "decreased low use" trajectory, the Medicare program could save $83.3 million (95% confidence interval: $58.5 million-$112.2 million).

Physician peer groups had distinct trajectories of abandoning CF-WBI. Physician composition and setting of radiotherapy were associated with the different trajectories. Distinct practice patterns across the trajectories had important cost implications.