title: Single or multi-channel vaginal cuff high-dose-rate brachytherapy: Is replanning necessary prior to each fraction?
abstract: OBJECTIVE
  Adjuvant high-dose-rate vaginal brachytherapy (VB) is commonly used in endometrial cancer. We evaluated the dosimetric and cost differences of using either a single plan or replan prior to each fraction for single- and multi-channel VB.
  
  
  METHODS
  We evaluated 84 fractions from 25 patients at our institution (16 single-channel patients each 3 fractions; 9 multi-channel patients each 4 fractions). All fractions were preceded by a computed tomographic (CT) simulation scan, after which a unique treatment plan was generated, dose points per International Commission on Radiation Units and Measurements (ICRU) 38. We calculated the dose to critical organs based on a decay-and-treat method utilizing the original catheter dwell-times for the initial fraction, and also the interfractional motion of the critical organ points between the initial and the subsequent CT scans.
  
  
  RESULTS
  The absolute mean dose difference was 14 cGy for bladder and 15 cGy for rectum between the replan and decay methods for single-channel, and 14 cGy for both organ points for the multi-channel cylinder. The bladder and rectum doses were not found to be significantly different between the replan and decay methods for either single-channel (bladder, P = .08; rectum, P = .19) or multi-channel cylinders (bladder, P = .85; rectum, P = .10). The mean interfractional displacement of the organ points between the initial and subsequent CT scans was 1.10 cm for the bladder and 0.67 cm for the rectum for single-channel, and 0.87 cm and 0.51 cm for multi-channel cylinders. The maximum interfractional motion was seen in the transverse plane for both organ points for both types of cylinders. At our institution, the decay method was 19% and 22% more cost-effective for single-channel and multi-channel cylinders, respectively.
  
  
  CONCLUSIONS
  Our data show no dosimetric advantage, but higher costs, associated with replanning prior to each fraction for both single- and multi-channel VB. Fractional replanning should not be utilized on a routine basis.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Jessica
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Joann
authors.initials: J
authors.lastname: Prisciandaro
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Choonik
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Matthew
authors.initials: M
authors.lastname: Schipper
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Avraham
authors.initials: A
authors.lastname: Eisbruch
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan. Electronic address: shrutij@med.umich.edu.
authors.forename: Shruti
authors.initials: S
authors.lastname: Jolly
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D016889:Endometrial Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000033:anatomy & histology / Q000528:radiation effects; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000528:radiation effects; D014621:Vagina