Implementation of ultra-hypofractionated radiotherapy for breast cancer in the Netherlands in 2020–2023, using registry data and questionnaires

Abstract Background This study investigated the implementation of ultra-hypofractionated radiotherapy (i.e. 5 fractions) in DCIS and early-stage breast cancer, factors associated with its use, and variation across radiotherapy institutes. Methods Registry and questionnaire data were used. Registry data included data from the Netherlands Cancer Registry and the NABON Breast Cancer Audit-Radiotherapy (NBCA-R). Women eligible for 5 fractions were included. Trends and variation were visualised using trendlines and case-mix adjusted boxplots. Logistic regression was applied to investigate which factors were associated with the use of 5 fractions. In April 2024 a questionnaire was distributed among radiotherapy institutes to identify facilitators and barriers for implementation. Results The current study included 16,115 women. In 2020, 18.5% of the eligible women received 5 fractions, compared to 60.8% in 2023. The lowest variation between radiotherapy institutes was found in 2023 (median: 60.4%, interquartile range: 53.3–70.6%). Age, tumour grade, multifocality, (y)pT, (y)pN, radiotherapy target volume, type of radiotherapy institute, and start year of radiation were associated with the chance of receiving 5 fractions. Sixteen out of the 19 radiotherapy institutes completed the questionnaire, showing variation in age and radiotherapy target volume for which the schedule was used. Most institutes mentioned no barriers for using 5 fractions. Questionnaire data confirmed the trendline finding that national consensus meetings were essential for largescale implementation. Conclusions The use of ultra-hypofractionated radiotherapy has increased during the past four years, with reduced variation across Dutch institutes. Registry and questionnaire data indicated that national consensus meetings were instrumental in driving implementation.