title: Second Cancer Risk after simultaneous integrated boost radiation therapy of right sided breast cancer with and without flattening filter.
abstract: BACKGROUND
  The aim of this study was to investigate if the flattening filter free mode (FFF) of a linear accelerator reduces the excess absolute risk (EAR) for second cancer as compared to the flat beam mode (FF) in simultaneous integrated boost (SIB) radiation therapy of right-sided breast cancer.
  
  
  METHODS
  Six plans were generated treating the whole breast to 50.4 Gy and a SIB volume to 63 Gy on CT data of 10 patients: intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and a tangential arc VMAT (tVMAT), each with flattening filter and without. The EAR was calculated for the contralateral breast and the lungs from dose-volume histograms (DVH) based on the linear-exponential, the plateau, and the full mechanistic dose-response model. Peripheral low-dose measurements were performed to compare the EAR in more distant regions as the thyroids and the uterus.
  
  
  RESULTS
  FFF reduces the EAR significantly in the contralateral and peripheral organs for tVMAT and in the peripheral organs for VMAT. No reduction was found for IMRT. The lowest EAR for the contralateral breast and lung was achieved with tVMAT FFF, reducing the EAR by 25 % and 29 % as compared to tVMAT FF, and by 44 % to 58 % as compared to VMAT and IMRT in both irradiation modes. tVMAT FFF showed also the lowest peripheral dose corresponding to the lowest EAR in the thyroids and the uterus.
  
  
  CONCLUSIONS
  The use of FFF mode allows reducing the EAR significantly when tVMAT is used as the treatment technique. When second cancer risk is a major concern, tVMAT FFF is considered the preferred treatment option in SIB irradiation of right-sided breast cancer.
authors.affiliation: Department of Radiotherapy, Regensburg University Medical Center, 93042, Regensburg, Germany. barbara.dobler@ukr.de.
authors.forename: Barbara
authors.initials: B
authors.lastname: Dobler
authors.affiliation: Department of Radiotherapy, Regensburg University Medical Center, 93042, Regensburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Maier
authors.affiliation: Department of Radiotherapy, Regensburg University Medical Center, 93042, Regensburg, Germany.
authors.forename: Bernadette
authors.initials: B
authors.lastname: Knott
authors.affiliation: Department of Radiotherapy, Regensburg University Medical Center, 93042, Regensburg, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Maerz
authors.affiliation: Faculty of Computer Science and Mathematics, Ostbayerische Technische Hochschule Regensburg, Regensburg, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Loeschel
authors.affiliation: Department of Radiotherapy, Regensburg University Medical Center, 93042, Regensburg, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Koelbl
mesh_terms: D000328:Adult; D000368:Aged; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced / Q000209:etiology* / Q000517:prevention & control*; D000069473:Radiation Dose Hypofractionation; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods*; D012307:Risk Factors; D016896:Treatment Outcome; D000069584:Unilateral Breast Neoplasms / Q000150:complications / Q000532:radiotherapy*
keywords: Breast Cancer; Flattening Filter Free; Peripheral Dose; Radiotherapy; Second Cancer Risk