Emergence of Single-Week Adjuvant Radiation Therapy for Early-Stage Breast Cancer in the United States

Over the past 2 decades, adjuvant radiation therapy (RT) for early-stage breast cancer has shifted toward shorter regimens. While initially occurring over 5 to 6 weeks, level 1 evidence has supported the equivalence of 3 to 4 weeks of adjuvant RT. More recently, level 1 evidence has demonstrated equivalence of 1-week ultrahypofractionated RT (UHRT) to 3-week adjuvant RT. This study evaluates the adoption of UHRT in the United States before, during, and after the COVID-19 pandemic.

Patients with early-stage breast cancer who received lumpectomy and adjuvant RT from 2018 to 2022 were assessed using the National Cancer Database (NCDB). UHRT was defined as 5.2 Gy per fraction with a total dose of 26 Gy. Data were grouped as prepandemic (2018 to 2019), pandemic (2020), and postpandemic (2021 to 2022). The adoption of UHRT and RT completion rates was assessed among these periods.

Before, during, and after the pandemic, 0.98% (133/13,154), 4.88% (303/6208), and 14.27% of patients (2044/14,321) underwent UHRT, respectively (P<0.0001). Cumulative RT completion rates were 94.85% before the pandemic, 96.10% during the pandemic, and 96.83% after the pandemic (P<0.0001), demonstrating a significant increase in adoption. For UHRT, completion rates were 100.00% prepandemic, 99.34% during the pandemic, and 99.46% postpandemic (P=0.6651), higher than overall RT completion rates across all 3 periods.

Nationwide data demonstrates a 14-fold increase in the use of UHRT from 2018 to 2022. Despite this increase and the near 100% completion rates for UHRT, UHRT remains underutilized compared with standard and hypofractionated regimens. These findings indicate fertile ground for increased UHRT adoption in breast cancer care nationwide.