title: Potentials of robust intensity modulated scanning proton plans for locally advanced lung cancer in comparison to intensity modulated photon plans.
abstract: OBJECTIVE
  The potentials of lung sparing, dose escalation, and the robustness of intensity modulated proton plans (IMPT(robust)), obtained by minimax optimization on multiple scenarios, were studied.
  
  
  METHODS
  IMPT(robust) optimization as described by Fredriksson et al. [23] was evaluated by means of comparative treatment planning using breath hold CT data from 6 non-small cell lung cancer (NSCLC) patients. IMPT(robust) and single field uniform dose (SFUD) proton plans were compared to Tomotherapy and 7-field intensity modulated photon therapy (IMXT). Plan robustness against set-up errors, range uncertainties, and between field motions were analyzed as well as lung exposure quantified by the mean lung dose (MLD) and the partial lung volumes receiving at least 20, 10, and 5 Gy(RBE) (V20, V10, V5). Robustness was analyzed with regard to stability of the effective uniform dose (EUD) and the dose level reached or exceeded in 95% of the CTV (D95).
  
  
  RESULTS
  MLD by IMPT(robust) was less than by SFUD, and Tomotherapy in each patient, on average by 14.8% and 28.5% (p<0.05, Friedman test). V20-V5 were higher with Tomotherapy compared to both proton therapy techniques, on average by a factor of >1.8. Robustness of IMPT(robust) was high. EUD and D95 values were maintained above 96% and 94% of the reference plan values for all tested scenarios. With dose escalation to 86 Gy(RBE) lung tissue tolerances were maintained.
  
  
  CONCLUSIONS
  IMPT(robust) proved advantageous in terms of lung exposure and possible dose escalation while being also markedly robust. However, motion during delivery of a field remains a major problem of IMPT(robust) to be mitigated by high scanning speed and variable spot size.
authors.affiliation: Department of Radiotherapy, University Hospital Essen, Essen, Germany, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Stuschke
authors.forename: Andreas
authors.initials: A
authors.lastname: Kaiser
authors.forename: Christoph
authors.initials: C
authors.lastname: Pöttgen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lübcke
authors.forename: Jonathan
authors.initials: J
authors.lastname: Farr
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D011522:Protons
chemical_list: D011522:Protons