title: Simultaneous integrated boost (SIB) radiation therapy of right sided breast cancer with and without flattening filter - A treatment planning study.
abstract: BACKGROUND
  The aim of the study was to compare the two irradiation modes with (FF) and without flattening filter (FFF) for three different treatment techniques for simultaneous integrated boost radiation therapy of patients with right sided breast cancer.
  
  
  METHODS
  An Elekta Synergy linac with Agility collimating device is used to simulate the treatment of 10 patients. Six plans were generated in Monaco 5.0 for each patient treating the whole breast and a simultaneous integrated boost (SIB) volume: intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT) and a tangential arc VMAT (tVMAT), each with and without flattening filter. Plan quality was assessed considering target coverage, sparing of the contralateral breast, the lungs, the heart and the normal tissue. All plans were verified by a 2D-ionisation-chamber-array and delivery times were measured and compared. The Wilcoxon test was used for statistical analysis with a significance level of 0.05.
  
  
  RESULTS
  Significantly best target coverage and homogeneity was achieved using VMAT FFF with V95% = (98.7 ± 0.8) % and HI = (8.2 ± 0.9) % for the SIB and V95% = (98.3 ± 0.7) % for the PTV, whereas tVMAT showed significantly lowest doses to the contralateral organs at risk with a Dmean of (0.7 ± 0.1) Gy for the contralateral lung, (1.0 ± 0.2) Gy for the contralateral breast and (1.4 ± 0.2) Gy for the heart. All plans passed the gamma evaluation with a mean passing rate of (99.2 ± 0.8) %. Delivery times were significantly reduced for VMAT and tVMAT but increased for IMRT, when FFF was used. Lowest delivery times were observed for tVMAT FFF with (1:20 ± 0:07) min.
  
  
  CONCLUSIONS
  Balancing target coverage, OAR sparing and delivery time, VMAT FFF and tVMAT FFF are considered the preferable of the investigated treatment options in simultaneous integrated boost irradiation of right sided breast cancer for the combination of an Elekta Synergy linac with Agility and the treatment planning system Monaco 5.0.
authors: Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
authors: Johannes
authors: J
authors: Maier
authors: Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
authors: Bernadette
authors: B
authors: Knott
authors: Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
authors: Manuel
authors: M
authors: Maerz
authors: Ostbayerische Technische Hochschule Regensburg, Faculty of Computer Science and Mathematics, Regensburg, Germany.
authors: Rainer
authors: R
authors: Loeschel
authors: Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
authors: Oliver
authors: O
authors: Koelbl
authors: Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany. barbara.dobler@ukr.de.
authors: Barbara
authors: http://orcid.org/0000-0002-3837-5137
authors: B
authors: Dobler
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D000069584:Unilateral Breast Neoplasms / Q000532:radiotherapy*