Variation in the use of ultra-hypofractionated irradiation in breast cancer in the Netherlands during the COVID-19 pandemic

Purpose Follow-up studies supporting the use of ultra-hypofractionated radiotherapy schemes, along with international COVID-19 guidelines indicating the implementation of these schemes and the first COVID-19 cases in the Netherlands in 2020 brought the ultra-hypofractionated schemes to attention. However, the extent of the implementation of these schemes in the Netherlands is unclear. This study aims to investigate the variation in the use of irradiation schemes, including the implementation of ultra-hypofractionated schemes and the factors influencing the chance of receiving ultra-hypofractionated radiotherapy. In addition, the reasoning behind radiotherapy institutions’ decisions to implement ultra-hypofractionated schemes in specific cases was investigated. Methods Non-metastatic, female patients with invasive breast cancer or DCIS, 18 years and older, who received postoperative RT between January 2020 and December 2021 and who were registered in the Netherlands Cancer Registry and the NABON Breast Cancer Audit Radiotherapy were included. Data analysis for 9599 tumours was done to determine the implementation of the RT schemes over time, logistic regression was used to determine which factors were associated with the implementation of ultra-hypofractionated schemes. A questionnaire was distributed among all Dutch radiotherapy institutes (n=19) to determine the reasoning of these institutes behind the implementation of the ultra-hypofractionated schemes. Results In 2021, the ultra-hypofractionated schemes were implemented to a larger extent and with more variation between radiotherapy institutes compared to 2020. According to the data analysis and questionnaire, at the start of the COVID-19 pandemic in the Netherlands, the ultra-hypofractionated schemes peaked in use, especially the 5x5.2 Gy (with 42 patients in April 2020) and the 5x5.7 Gy (with 55 patients in May 2020) schemes. These peaks were due to the institutions’ desire to reduce the pressure on healthcare and to prevent infections. From June 2020, the 5x5.2 Gy scheme increased in use and from March 2021 the 5x5.7 Gy scheme decreased. The patient’s age, tumour size, lymph node involvement, type of RT centre, PBI treatment and the period of administration were significantly associated with the implementation of ultra-hypofractionated schemes (5x5.2 Gy, 5x5.7 Gy, 5x6 Gy) according to the logistic regression. Most indicated factors influencing the implementation of these schemes according to the questionnaire were dosimetric homogeneity, wound (healing) problems and (large) seromas. Conclusion The use of ultra-hypofractionated schemes, especially the 5x5.2 and 5x5.7 Gy schemes, has increased for nonmetastatic surgically treated breast cancer patients after March 2020. Low-risk patients, university-related RT institutes, PBI treatment, the start of the COVID-19 pandemic and the LPRM meetings were influencing factors on whether to implement the ultra-hypofractionated schemes. The RT institutes indicated that (large) seromas, wound problems and dosimetric inhomogeneity were frequently answered factors not to implement the schemes.