title: Assessing the robustness of passive scattering proton therapy with regard to local recurrence in stage III non-small cell lung cancer: a secondary analysis of a phase II trial.
abstract: BACKGROUND
  We assessed the robustness of passive scattering proton therapy (PSPT) plans for patients in a phase II trial of PSPT for stage III non-small cell lung cancer (NSCLC) by using the worst-case scenario method, and compared the worst-case dose distributions with the appearance of locally recurrent lesions.
  
  
  METHODS
  Worst-case dose distributions were generated for each of 9 patients who experienced recurrence after concurrent chemotherapy and PSPT to 74 Gy(RBE) for stage III NSCLC by simulating and incorporating uncertainties associated with set-up, respiration-induced organ motion, and proton range in the planning process. The worst-case CT scans were then fused with the positron emission tomography (PET) scans to locate the recurrence.
  
  
  RESULTS
  Although the volumes enclosed by the prescription isodose lines in the worst-case dose distributions were consistently smaller than enclosed volumes in the nominal plans, the target dose coverage was not significantly affected: only one patient had a recurrence outside the prescription isodose lines in the worst-case plan.
  
  
  CONCLUSIONS
  PSPT is a relatively robust technique. Local recurrence was not associated with target underdosage resulting from estimated uncertainties in 8 of 9 cases.
authors.forename: Zhengfei
authors.initials: Z
authors.lastname: Zhu
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Michael
authors.initials: M
authors.lastname: Gillin
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Gomez
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
authors.forename: James D
authors.initials: JD
authors.lastname: Cox
authors.forename: Radhe
authors.initials: R
authors.lastname: Mohan
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. jychang@mdanderson.org.
authors.forename: Joe Y
authors.initials: JY
authors.lastname: Chang
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology* / Q000532:radiotherapy*; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis*; D009367:Neoplasm Staging; D011379:Prognosis; D011446:Prospective Studies; D061766:Proton Therapy; D012189:Retrospective Studies; D015996:Survival Rate