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@ARTICLE{Unkelbach:136905,
      author       = {J. Unkelbach and M. Bangert$^*$ and K. De Amorim Bernstein
                      and N. Andratschke and M. Guckenberger},
      title        = {{O}ptimization of combined proton-photon treatments.},
      journal      = {Radiotherapy and oncology},
      volume       = {128},
      number       = {1},
      issn         = {0167-8140},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier Science},
      reportid     = {DKFZ-2018-01343},
      pages        = {133 - 138},
      year         = {2018},
      abstract     = {Proton treatment slots are a limited resource. Therefore,
                      we consider combined proton-photon treatments in which most
                      fractions are delivered with photons and only a few with
                      protons. We demonstrate how both modalities can be combined
                      to optimally capitalize on the proton's ability to reduce
                      normal tissue dose.An optimal combined treatment must
                      account for fractionation effects. We therefore perform
                      simultaneous optimization of intensity-modulated proton
                      (IMPT) and photon (IMRT) plans based on their cumulative
                      biologically effective dose (BED). We demonstrate the method
                      for a sacral chordoma patient, in whom the gross tumor
                      volume (GTV) abuts bowel and rectum.In an optimal
                      combination, proton and photon fractions deliver similar
                      doses to bowel and rectum to protect these dose-limiting
                      normal tissues through fractionation. However, proton
                      fractions deliver, on average, higher doses to the GTV.
                      Thereby, the photon dose bath is reduced. An optimized
                      30-fraction treatment with 10 IMPT fractions achieved more
                      than $50\%$ of the integral dose reduction in the
                      gastrointestinal tract that is possible with 30 IMPT
                      fractions (compared to $33\%$ for a simple proton-photon
                      combination in which both modalities deliver the same target
                      dose).A limited number of proton fractions can best be used
                      if protons hypofractionate parts of the GTV while
                      maintaining near-uniform fractionation in dose-limiting
                      normal tissues.},
      cin          = {E040},
      ddc          = {610},
      cid          = {I:(DE-He78)E040-20160331},
      pnm          = {315 - Imaging and radiooncology (POF3-315)},
      pid          = {G:(DE-HGF)POF3-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:29370987},
      doi          = {10.1016/j.radonc.2017.12.031},
      url          = {https://inrepo02.dkfz.de/record/136905},
}