title: Pelvic lymph node displacement in high-risk prostate cancer patients treated with image guided intensity modulated radiation therapy with 2 independent target volumes.
abstract: OBJECTIVE
  To evaluate the displacement of the pelvic lymph node (PLN) target when using cone beam computed tomography (CBCT) for localization of the prostate in patients treated with simultaneous integrated boost.
  
  
  METHODS
  High-risk prostate cancer patients treated with image guided intensity modulated radiation therapy with simultaneous integrated boost receiving 60 Gy in 20 fractions to the prostate and proximal seminal vesicles (PTV60) and 44 Gy in the same 20 fractions to the PLN (PTV44) were studied. Two hundred weekly CBCTs of 50 patients were retrospectively reviewed to assess the displacement of the iliac vessels compared with the simulation computed tomography. For each CBCT, possible displacements were analyzed at 3 levels of PTV44: a superior, middle, and inferior slice, making a total of 600 slices reviewed. Geographical miss (GM) was defined when any part of the iliac vessels on the CBCT was outside of the PTV44 contour.
  
  
  RESULTS
  GM was found in 7 of the 600 CBCT slices, all in different patients. All GMs were of ≤5 mm. Four GMs occurred on the middle slice and 3 on the superior slice. In 3 cases, the GM was related to shifts ≥7 mm applied to the prostate.
  
  
  CONCLUSIONS
  Our review suggests that for high-risk prostate cancer, the chance of not appropriately covering the PLN target after adjusting the prostate is low. GM was uncommon and in the order of only a few millimeters when it occurred.
authors.affiliation: Department of Radiation Oncology, McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.
authors.forename: Magali
authors.initials: M
authors.lastname: Lecavalier-Barsoum
authors.affiliation: Department of Radiation Oncology, McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.
authors.forename: Luis
authors.initials: L
authors.lastname: Souhami
authors.affiliation: Department of Radiation Oncology, McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.
authors.forename: Fabio
authors.initials: F
authors.lastname: Cury
authors.affiliation: Department of Radiation Oncology, McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.
authors.forename: Marie
authors.initials: M
authors.lastname: Duclos
authors.affiliation: Department of Medical Physics, McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.
authors.forename: Russel
authors.initials: R
authors.lastname: Ruo
authors.affiliation: Department of Radiation Oncology, McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada. Electronic address: sergio.faria@muhc.mcgill.ca.
authors.forename: Sergio
authors.initials: S
authors.lastname: Faria
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D054893:Cone-Beam Computed Tomography; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology* / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D058958:Organs at Risk; D010386:Pelvic Neoplasms / Q000473:pathology* / Q000532:radiotherapy; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden