Abstract Background The aim of the study was to identify factors significantly associated with the occurrence of unintended treatment interruptions in adjuvant breast cancer radiotherapy. Patients and methods Patients treated with postoperative radiotherapy of the breast or chest wall between March 2014 and August 2016 were evaluated. The radiotherapy regimens and techniques applied were either conventional fractionation (CF; 28 daily fractions of 1.8Gy or 25 fractionsof2.0Gy)orhypofractionation(HF;15dailyfractions of2.67Gy)withinverseplannedintensity-modulatedradiotherapy(IMRT)orthree-dimensionalplannedconformalradiotherapy (3DCRT). Logistic regression analysis was used to identify factors associated with noncompliance. Noncompliancewasdefinedasthemissingofatleastonescheduled radiotherapy fraction. Results In all, 19 of 140 (13.6%) patients treated with HF and 39 of 146 (26.7%) treated with CF experienced treatment interruptions. Of 23 factors tested, the fractionation regimen emerged as the only independent significant prognostic factor for noncompliance on multivariate analysis (CF; p = 0.007; odds ratio, 2.3; 95% confidence interval,  Prof. Dr. med. Volker Rudat vrudat@saadmedical.com, volker.rudat@gmail.com Alaa Nour ANour@saadmedical.com Mohamed Hammoud MHammoud@saadmedical.com Salam Abou Ghaida SAbouGhaida@saadmedical.com 1 Department of Radiation Oncology, Saad Specialist Hospital, 31952 Al Khobar, Saudi Arabia 1.3–4.2). No statistically significant differences concerning the reasons for treatment interruptions could be detected between patients treated with CF or HF. Conclusion HF is significantly associated with a better patient compliance with the prescribed radiotherapy schedule compared with CF. The data suggest that this finding is basically related to the shorter overall treatment time of HF.
Keywords Breast neoplasms · Radiotherapy · Dose hypofractionation · Radiation injuries · Risk factors