National real-world adoption of 5-fraction breast radiotherapy in the United States (2020–2023).

590 Background: The landmark FAST-Forward trial demonstrated that ultra-hypofractionated whole-breast irradiation with 26 Gy in 5 fractions over 1 week was non-inferior to 40 Gy in 15 fractions for local control (HR 0.67, 95% CI 0.38–1.16), with similar normal tissue effects at 5 years. In response, major international guidelines incorporated 26 Gy in 5 fractions as a standard approach or recommended option for selected patients. Despite robust randomized evidence and guideline endorsement, U.S. real-world adoption patterns and equity of uptake across patient populations remain incompletely characterized. This study evaluated national trends in 5-fraction breast radiotherapy and sociodemographic differences from 2020 to 2023. Methods: The National Cancer Database radiotherapy fractionation fields were used to identify radiotherapy (RT) courses with evaluable fraction counts, and a binary indicator for 5-fraction RT (yes/no) was created. Temporal trends by diagnosis year (2020–2023) were assessed, and associations between 5-fraction RT and sociodemographic factors (primary insurance, urban or rural status, neighborhood income quartile, and race) were examined using chi-square testing. Results: Among 536,783 RT courses with complete data from 2020 to 2023, use of 5-fraction RT increased substantially over time: 4.3% in 2020, 8.1% in 2021, 12.7% in 2022, and 17.4% in 2023, resulting in an overall adoption rate of 10.7% (p < 0.001). In the subset eligible for fractionation (5, 15–16, 25–28 fractions; N = 31,448), 5-fraction RT accounted for 11.7% and differed significantly by insurance type (p < 0.001): Medicare 17.4%, Private 7.6%, Medicaid 5.9%, and Uninsured 6.9%. Geographic variation was notable (p < 0.001), ranging from 7.3% in mid-size metropolitan areas (250,000–1 million population) to 17.7%–18.1% in more remote or non-adjacent areas; large metropolitan areas (≥1 million) had 12.8% uptake. Neighborhood income showed a gradient (p < 0.001): 10.1% in the lowest quartile compared to 12.5% in the highest. Race was also associated with uptake (p < 0.001), with lower use among Black patients compared to White patients (9.4% vs 12.2%). Conclusions: In routine U.S. practice, adoption of 5-fraction breast RT increased rapidly from 2020 to 2023, with the most pronounced growth after 2021, reflecting the swift translation of trial evidence into clinical practice. However, uptake varies by insurance, geography, income, and race, indicating that diffusion is not uniform. Given the potential benefits of ultra-hypofractionation in reducing treatment burden and supporting timely completion, targeted implementation strategies, such as provider education, reimbursement alignment, and facility-level operational support, may be necessary to ensure equitable access as 5-fraction regimens become more widely adopted and potentially become the standard of care.