Guido Hildebrandt1, Angrit Stachs2, Bernd Gerber2, Jochem Potenberg3, David Krug4, Kathi Wolter1, Thorsten Kühn5, Dietmar Zierhut6, Felix Sedlmayer7, Julia Kaiser7, Roland Reitsamer8, Jörg Heil9, Valentina Nekljudova10, Inga Bekes11, Sibylle Loibl10, Toralf Reimer12. 1. Department of Radiotherapy, University of Rostock, Rostock, Germany. 2. Department of Obstetrics and Gynecology, University of Rostock, Rostock, Germany. 3. Breast Center, Evangelisches Waldkrankenhaus Spandau, Berlin, Germany. 4. Department of Radiation Oncology, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany. 5. Department of Obstetrics and Gynecology, Interdisciplinary Breast Center, Esslingen, Germany. 6. Department of Radio-Oncology and Radiotherapy, Klinikum Hanau GmbH, Hanau, Germany. 7. Department of Radiotherapy and Radio-Oncology, LKH Salzburg, Paracelsus Medical University Clinics, Salzburg, Austria. 8. Breast Center, LKH Salzburg, Paracelsus Medical University Clinics, Salzburg, Austria. 9. Breast Unit, University Hospital, University of Heidelberg, Heidelberg, Germany. 10. German Breast Group, Neu-Isenburg, Germany. 11. Department of Obstetrics and Gynecology, University of Ulm, Ulm, Germany. 12. Department of Obstetrics and Gynecology, University of Rostock, Rostock, Germany. Electronic address: toralf.reimer@med.uni-rostock.de.
Abstract
PURPOSE: After publication of the radiation field design in the American College of Surgeons Oncology Group Z0011 trial, a radiation therapy quality assurance review was integrated into the Intergroup-Sentinel-Mamma (INSEMA) trial. We aimed to investigate the role of patient characteristics, extent of axillary surgery, and radiation techniques for dose distribution in ipsilateral axillary levels. METHODS AND MATERIALS: INSEMA (NCT02466737) has randomized 5542 patients who underwent breast-conserving surgery. Of these, 276 patients from 108 radiation therapy facilities were included in the central review, using the planning records of the first 3 patients treated at each site. RESULTS: Of the 276 patients, 41 had major deviations (ie, no axillary contouring or submission of insufficient records) leading to exclusion. A total of 235 (85.1%) radiation therapy planning records were delineated according to the INSEMA protocol, including 9 (3.8%) cases with minor deviations. At least 25% of INSEMA patients were unintentionally treated with ≥95% of the prescribed breast radiation dose in axillary level I. Approximately 50% of patients were irradiated with a median radiation dose of more than 85% of prescription dose in level I. Irradiated volumes and applied doses were significantly lower in levels II and III compared with level I. However, 25% of patients still received a median radiation dose of ≥75% of prescription dose to level II. Subgroup analysis revealed a significant association between incidental radiation dose in the axilla and obesity. Younger age, boost application, and fractionation schedule showed no impact on axillary dose distribution. CONCLUSIONS: Assuming ≥80% of prescribed breast dose as the optimal dose for curative radiation of low-volume disease in axillary lymph nodes, at least 50% of reviewed INSEMA patients received an adequate dose in level I, even with contemporary 3-dimensional techniques. Dose coverage was much less in axillary levels II and III, and far below therapeutically relevant doses.
PURPOSE: After publication of the radiation field design in the American College of Surgeons Oncology Group Z0011 trial, a radiation therapy quality assurance review was integrated into the Intergroup-Sentinel-Mamma (INSEMA) trial. We aimed to investigate the role of patient characteristics, extent of axillary surgery, and radiation techniques for dose distribution in ipsilateral axillary levels. METHODS AND MATERIALS: INSEMA (NCT02466737) has randomized 5542 patients who underwent breast-conserving surgery. Of these, 276 patients from 108 radiation therapy facilities were included in the central review, using the planning records of the first 3 patients treated at each site. RESULTS: Of the 276 patients, 41 had major deviations (ie, no axillary contouring or submission of insufficient records) leading to exclusion. A total of 235 (85.1%) radiation therapy planning records were delineated according to the INSEMA protocol, including 9 (3.8%) cases with minor deviations. At least 25% of INSEMA patients were unintentionally treated with ≥95% of the prescribed breast radiation dose in axillary level I. Approximately 50% of patients were irradiated with a median radiation dose of more than 85% of prescription dose in level I. Irradiated volumes and applied doses were significantly lower in levels II and III compared with level I. However, 25% of patients still received a median radiation dose of ≥75% of prescription dose to level II. Subgroup analysis revealed a significant association between incidental radiation dose in the axilla and obesity. Younger age, boost application, and fractionation schedule showed no impact on axillary dose distribution. CONCLUSIONS: Assuming ≥80% of prescribed breast dose as the optimal dose for curative radiation of low-volume disease in axillary lymph nodes, at least 50% of reviewed INSEMA patients received an adequate dose in level I, even with contemporary 3-dimensional techniques. Dose coverage was much less in axillary levels II and III, and far below therapeutically relevant doses.