title: IMRT of prostate cancer: a comparison of fluence optimization with sequential segmentation and direct step-and-shoot optimization.
abstract: OBJECTIVE
  Intensity-modulated radiation therapy (IMRT) has shown its superiority to three-dimensional conformal radiotherapy in the treatment of prostate cancer. Different optimization algorithms are available: algorithms which first optimize the fluence followed by a sequencing (IM), and algorithms which involve the machine parameters directly in the optimization process (DSS). The aim of this treatment-planning study is to compare both of them regarding dose distribution and treatment time.
  
  
  METHODS
  Ten consecutive patients with localized prostate cancer were enrolled for the planning study. The planning target volume and the rectum volume, urinary bladder and femoral heads as organs at risk were delineated. Average doses, the target dose homogeneity H, D(5), D(95), monitor units per fraction, and the number of segments were evaluated.
  
  
  RESULTS
  While there is only a small difference in the mean doses at rectum and bladder, there is a significant advantage for the target dose homogeneity in the DSS-optimized plans compared to the IM-optimized ones. Differences in the monitor units (nearly 10% less for DSS) and the number of segments are also statistically significant and reduce the treatment time.
  
  
  CONCLUSIONS
  Particularly with regard to the tumor control probability, the better homogeneity of the DSS-optimized plans is more profitable. The shorter treatment time is an improvement regarding intrafractional organ motion. The DSS optimizer results in a higher target dose homogeneity and, simultaneously, in a lower number of monitor units. Therefore, it should be preferred for IMRT of prostate cancer.
authors.affiliation: Department of Radiation Oncology, Regensburg University Medical Center, Regensburg, Germany. marius.treutwein@klinik.uni-regensburg.de
authors.forename: Marius
authors.initials: M
authors.lastname: Treutwein
authors.forename: Matthias
authors.initials: M
authors.lastname: Hipp
authors.forename: Oliver
authors.initials: O
authors.lastname: Kölbl
authors.forename: Ludwig
authors.initials: L
authors.lastname: Bogner
mesh_terms: D000368:Aged; D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D011786:Quality Control; D011879:Radiotherapy Dosage; D016896:Treatment Outcome