title: Node-positive left-sided breast cancer patients after breast-conserving surgery: potential outcomes of radiotherapy modalities and techniques.
abstract: OBJECTIVE
  To determine how much proton and intensity modulated photon radiotherapy (IMRT) can improve treatment results of node-positive left-sided breast cancer compared to conventional radiation qualities (X-rays and electrons) after breast-conserving surgery in terms of lower complication risks for cardiac mortality and radiation pneumonitis.
  
  
  METHODS
  For each of 11 patient studies, one proton plan, one IMRT, and two conventional (tangential and patched) plans were calculated using a three-dimensional treatment-planning system, Helax-TMS(). The evaluation of the different treatment plans was made by applying the normal tissue complication probability model (NTCP) proposed by Källman (also denoted the relative seriality model) on the dose distributions in terms of dose-volume histograms. The organs at risk are the spinal cord, the left lung, the heart, and the non-critical normal tissues (including the right breast).
  
  
  RESULTS
  The comparison demonstrated that the proton treatment plans provide significantly lower NTCP values for the heart and lung when compared to conventional radiation qualities including IMRT for all 11 patients. At a prescribed dose of 50 Gy in the PTV, the calculated mean NTCP value for the patients decreased, on the average, from 14.7 to 0.6% for the lung (radiation pneumonitis) for the proton plans compared with the best plan using conventional radiation qualities. The corresponding figures for the heart (cardiac mortality) were from 2.1 to 0.5%. The figures for cardiac mortality for IMRT, tangential technique and the patched technique were 2.2, 6.7, and 2.1%, respectively.
  
  
  CONCLUSIONS
  Protons appear to have major advantages in terms of lower complication risks when compared with treatments using conventional radiation qualities for treating node-positive left-sided breast cancer after breast-conserving surgery.
authors.affiliation: Section of Oncology, Ing 78, University of Uppsala, Akademiska sjukhuset, SE 75185 Uppsala, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Johansson
authors.forename: Ulf
authors.initials: U
authors.lastname: Isacsson
authors.forename: Henrik
authors.initials: H
authors.lastname: Lindman
authors.forename: Anders
authors.initials: A
authors.lastname: Montelius
authors.forename: Bengt
authors.initials: B
authors.lastname: Glimelius
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D003131:Combined Modality Therapy; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006331:Heart Diseases / Q000209:etiology / Q000517:prevention & control; D006801:Humans; D015182:Lymphatic Irradiation / Q000009:adverse effects / Q000379:methods*; D008207:Lymphatic Metastasis; D008875:Middle Aged; D011336:Probability; D011522:Protons; D017564:Radiation Pneumonitis / Q000209:etiology / Q000517:prevention & control; D016896:Treatment Outcome
chemical_list: D011522:Protons