title: Tumor and normal tissue dosimetry changes during MR-guided pulsed-dose-rate (PDR) brachytherapy for cervical cancer.
abstract: OBJECTIVE
  To analyze systematic changes in tumor and normal tissue anatomy and dosimetry using serial MR imaging during pulsed dose rate brachytherapy (PDR BT) for cervical cancer.
  
  
  METHODS
  Forty-three patients with cervical cancer underwent MR-guided PDR BT using an intrauterine applicator alone after external beam radiotherapy. MR imaging was repeated on days 2 and 3 of treatment and the day 1 plan was applied to the re-contoured volumes.
  
  
  RESULTS
  The mean uterine volume and mean HR CTV increased during treatment. This resulted in a decrease in the mean HR CTV D90 relative to the day 1 planned dose. There was no change in the mean bladder volume during treatment but the mean rectal volume increased. This correlated with an increase in the mean rectal dose. There were four local recurrences. There was no apparent relationship between either the planned or the delivered HR CTV D90 and local recurrence. There was only one case of late bladder toxicity but nine patients developed late rectal toxicity. The cumulative rectal dose during treatment was a better predictor of late rectal toxicity than the planned dose.
  
  
  CONCLUSIONS
  Significant changes in tumor and normal tissue anatomy and dosimetry can occur during PDR BT and should be tracked and corrected using serial imaging and plan adaptation, especially when the day 1 tumor or normal tissue doses are close to the planning constraints.
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre/University Health Network, Toronto, Canada.
authors.forename: Marita
authors.initials: M
authors.lastname: Morgia
authors.forename: Julie
authors.initials: J
authors.lastname: Cuartero
authors.forename: Lorraine
authors.initials: L
authors.lastname: Walsh
authors.forename: John
authors.initials: J
authors.lastname: Jezioranski
authors.forename: Kirsten
authors.initials: K
authors.lastname: Keeler
authors.forename: Jason
authors.initials: J
authors.lastname: Xie
authors.forename: Christine
authors.initials: C
authors.lastname: Massey
authors.forename: Debbie
authors.initials: D
authors.lastname: Williamson
authors.forename: Young-Bin
authors.initials: YB
authors.lastname: Cho
authors.forename: Seungjong
authors.initials: S
authors.lastname: Oh
authors.forename: Anthony
authors.initials: A
authors.lastname: Fyles
authors.forename: Michael
authors.initials: M
authors.lastname: Milosevic
mesh_terms: D000328:Adult; D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D008875:Middle Aged; D058958:Organs at Risk; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D047368:Tumor Burden; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*