Importance  Based on randomized evidence, expert guidelines in 2011 endorsed shorter, hypofractionated whole breast irradiation (WBI) for selected patients with early-stage breast cancer and permitted hypofractionated WBI for other patients.
Objectives  To examine the uptake and costs of hypofractionated WBI among commercially insured patients in the United States.
Design, Setting, and Participants  Retrospective, observational cohort study, using administrative claims data from 14 commercial health care plans covering 7.4% of US adult women in 2013, we classified patients with incident early-stage breast cancer treated with lumpectomy and WBI from 2008 and 2013 into 2 cohorts: (1) the hypofractionation-endorsed cohort (n = 8924) included patients aged 50 years or older without prior chemotherapy or axillary lymph node involvement and (2) the hypofractionation-permitted cohort (n = 6719) included patients younger than 50 years or those with prior chemotherapy or axillary lymph node involvement.
Exposures  Hypofractionated WBI (3-5 weeks of treatment) vs conventional WBI (5-7 weeks of treatment).
Main Outcomes and Measures  Use of hypofractionated and conventional WBI, total and radiotherapy-related health care expenditures, and patient out-of-pocket expenses. Patient and clinical characteristics included year of treatment, age, comorbid disease, prior chemotherapy, axillary lymph node involvement, intensity-modulated radiotherapy, practice setting, and other contextual variables.
Results  Hypofractionated WBI increased from 10.6% (95% CI, 8.8%-12.5%) in 2008 to 34.5% (95% CI, 32.2%-36.8%) in 2013 in the hypofractionation-endorsed cohort and from 8.1% (95% CI, 6.0%-10.2%) in 2008 to 21.2% (95% CI, 18.9%-23.6%) in 2013 in the hypofractionation-permitted cohort. Adjusted mean total health care expenditures in the 1 year after diagnosis were $28 747 for hypofractionated and $31 641 for conventional WBI in the hypofractionation-endorsed cohort (difference, $2894; 95% CI, $1610-$4234; P < .001) and $64 273 for hypofractionated and $72 860 for conventional WBI in the hypofractionation-permitted cohort (difference, $8587; 95% CI, $5316-$12 017; P < .001). Adjusted mean total 1-year patient out-of-pocket expenses were not significantly different between hypofractionated vs conventional WBI in either cohort.
Conclusions and Relevance  Hypofractionated WBI after breast conserving surgery increased among women with early-stage breast cancer in 14 US commercial health care plans between 2008 and 2013. However, only 34.5% of patients with hypofractionation-endorsed and 21.2% with hypofractionation-permitted early-stage breast cancer received hypofractionated WBI in 2013.