title: Lipiodol as a fiducial marker for image-guided radiation therapy for bladder cancer.
abstract: OBJECTIVE
  To evaluate Lipiodol as a liquid, radio-opaque fiducial marker for image-guided radiation therapy (IGRT) for bladder cancer.
  
  
  METHODS
  Between 2011 and 2012, 5 clinical T2a-T3b N0 M0 stage II-III bladder cancer patients were treated with maximal transurethral resection of a bladder tumor (TURBT) and image-guided radiation therapy (IGRT) to 64.8 Gy in 36 fractions ± concurrent weekly cisplatin-based or gemcitabine chemotherapy. Ten to 15mL Lipiodol, using 0.5mL per injection, was injected into bladder submucosa circumferentially around the entire periphery of the tumor bed immediately following maximal TURBT. The authors looked at inter-observer variability regarding the size and location of the tumor bed (CTVboost) on computed tomography scans with versus without Lipiodol.
  
  
  RESULTS
  Median follow-up was 18 months. Lipiodol was visible on every orthogonal two-dimensional kV portal image throughout the entire, 7-week course of IGRT. There was a trend towards improved inter-observer agreement on the CTVboost with Lipiodol (p = 0.06). In 2 of 5 patients, the tumor bed based upon Lipiodol extended outside a planning target volume that would have been treated with a radiation boost based upon a cystoscopy report and an enhanced computed tomography (CT) scan for staging. There was no toxicity attributable to Lipiodol.
  
  
  CONCLUSIONS
  Lipiodol constitutes a safe and effective fiducial marker that an urologist can use to demarcate a tumor bed immediately following maximal TURBT. Lipiodol decreases inter-observer variability in the definition of the extent and location of a tumor bed on a treatment planning CT scan for a radiation boost.
authors.affiliation: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Freilich
authors.affiliation: Department of Urology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Philippe E
authors.initials: PE
authors.lastname: Spiess
authors.affiliation: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Biagioli
authors.affiliation: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Daniel C C
authors.initials: DC
authors.lastname: Fernandez
authors.affiliation: Department of Data Quality and Standards, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Ellen J
authors.initials: EJ
authors.lastname: Shi
authors.affiliation: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Dylan C
authors.initials: DC
authors.lastname: Hunt
authors.affiliation: Department of Genitourinary Oncology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Gupta
authors.affiliation: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Wilder
mesh_terms: D000328:Adult; D002277:Carcinoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D003287:Contrast Media; D003558:Cystoscopy / Q000379:methods; D004998:Ethiodized Oil; D057918:Fiducial Markers; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D015588:Observer Variation; D011859:Radiography; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D047368:Tumor Burden; D001749:Urinary Bladder Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*
chemical_list: D003287:Contrast Media; D004998:Ethiodized Oil