Abandonment trajectories of conventionally fractionated adjuvant radiotherapy in breast cancer care.

Abstract

531 Background: Hypofractionated radiotherapy is the recommended approach for adjuvant breast cancer care. Yet physicians have been slow to abandon conventionally fractionated radiotherapy (CFRT). We examined distinct trajectories of abandoning CFRT among physician patient-sharing peer groups and the associated cost implications. Methods: Using 2011-2014 national Medicare claims, we constructed peer groups of physicians (radiation and medical oncologists, surgeons, and primary care physicians) who cared for women with breast cancer. Women ≥66 years of age who underwent lumpectomy plus adjuvant radiotherapy were included. Peer groups represented physicians who frequently shared patients with one another. For each peer group, we calculated risk-adjusted rate of CFRT use in 2011-2012 (T1) and 2013-2014 (T2) after accounting for patient risk factors. Based on these utilization rates and a latent growth curve analysis, we identified distinct trajectories of abandoning CFRT among peer groups and estimated their cost implications from the Medicare perspective. Results: The 215 physician peer groups (caring for 16,988 patients) exhibited four distinct trajectories of CFRT use: 1) persistent high use (mean adjusted utilization: T1 = 94.3%, T2 = 90.6%); 2) decreased high use (T1 = 81.3%, T2 = 65.3%); 3) decreased medium use (T1 = 60.1%, T2 = 44.0%); and 4) decreased low use (T1 = 31.6%, T2 = 23.6%). They accounted for 33.0%, 35.3%, 25.6% and 6.0% of the peer groups, respectively. Compared to “persistent high use” of CFRT, peer groups with “decreased high use” and “decreased medium use” of CFRT had a smaller proportion of patients receiving radiotherapy at free-standing (vs. hospital-based) facilities (adjusted odds ratio = 0.89, p = 0.01; and 0.78, p < 0.01; respectively). Accelerating abandonment of CFRT in the three higher utilization trajectories to “decreased low use” for the 2011-2014 patient cohort could save Medicare $342.7 million (95% confidence interval: $232.2-$457.6 million). Conclusions: Physician peer groups had distinct trajectories in abandoning CFRT exhibiting different baseline levels and rates of change in utilization. Efforts to reduce overuse of CFRT could generate substantial savings.