Background: American Society of Radiation Oncology Choosing Wisely campaign recommends hypofractionated radiation and against routine use of intensity-modulated radiation therapy (IMRT) in early-stage estrogen receptor-positive breast cancer. We analyzed guideline recommendation adherence and financial implications in a modern Medicare cohort of women treated across the southeastern United States. Methods: Our study population comprised Medicare patients over 65 years of age with breast cancer diagnosis from 12 cancer centers in the Southeast United States with stage 0-II breast treated with lumpectomy from 2012 to 2015. Hypofractionation was defined as 4 or fewer weeks of radiation treatments. Factors associated with utilization of hypofractionation and IMRT were identified using Poisson regression. Median costs during radiation treatments were compared for hypofractionation and IMRT. Results: In older women (median age 71), 75% were treated with conventional fractionation, and 20% received IMRT. Hypofractionated women were more likely to have a positive estrogen(ER) or progestorone(PR) receptor status, lower comorbidity scores, and be treated at a high volume center (all P < 0.05). IMRT was utilized in 20% of patients and was more common in women treated with conventional fractionation (P < 0.001). Positive ER/PR status (P < 0.001) and utilization of hormonal blockade (P = 0.02) were associated with increased utilization of IMRT. Conclusion: In an older cohort of patients with early-stage breast cancer, a majority were treated with conventional fractionated radiation, while approximately 20% were treated with IMRT. Both of which were associated with increased cost relative to hypofractionation.