Impact of guideline changes on adoption of hypofractionation and breast cancer patient characteristics in the randomized controlled HYPOSIB trial

Purpose!#!Hypofractionated radiotherapy is the standard of care for adjuvant whole breast radiotherapy (RT). However, adoption has been slow. The indication for regional nodal irradiation has been expanded to include patients with 0-3 involved lymph nodes. We investigated the impact of the publication of the updated German S3 guidelines in 2017 on adoption of hypofractionation and enrollment of patients with lymph node involvement within a randomized controlled phase III trial.!##!Methods!#!In the experimental arm of the HYPOSIB trial (NCT02474641), hypofractionated RT with simultaneous integrated boost (SIB) was used. In the standard arm, RT could be given as hypofractionated RT with sequential boost (HF!##!Results!#!Enrollment of patients with involved lymph nodes was low throughout the trial. Adoption of HF!##!Conclusion!#!The use of H