title: Target volume changes through high-dose-rate brachytherapy for cervical cancer when evaluated on high resolution (3.0 Tesla) magnetic resonance imaging.
abstract: OBJECTIVE
  To evaluate tumor volume changes that occurred during courses of high-dose-rate brachytherapy (HDR) using high resolution (3.0 Tesla) magnetic resonance imaging (MRI), along with the regression after external beam radiation therapy (EBRT).
  
  
  METHODS
  Fourteen patients with International Federation of Gynecology and Obstetrics stage IB1-IV cervical cancer were studied retrospectively. All patients underwent EBRT with concurrent chemotherapy followed by HDR brachytherapy. Gross tumor volume (GTV) and high-risk clinical target volume (HR-CTV) were contoured on a 3.0 Tesla MRI on the day of the HDR and on diagnostic MRI (1.5 Tesla) prior to EBRT. Two physicians independently contoured the GTV and HR-CTV on a total of 46 MRI data sets for the HDR plans. The percent volume changes of GTV and HR-CTV were quantified after EBRT and again after each HDR. The conformity indices (CIs) of the 2 contours were assessed.
  
  
  RESULTS
  GTV and HR-CTV considerably regressed after the first ( --31.7% ± 19.3% and --26.4% ± 6.9%, respectively) and the second (--26.8% ± 14.3% and --23.8% ± 11.0%) fraction of HDR while relatively small regressions were observed after the third (--16.3% ± 14.2% and --10.6% ± 13.4%) and the fourth (--8.0% ± 3.4% and --9.0% ± 8.0%) fractions. The lymph node-positive on positron emission tomography (PET) and stage III or IV group showed, on average, more than 200% larger GTV and HR-CTV before EBRT than those of the other patients. The GTV and HR-CTV for the group were larger on average more than 150% after EBRT and before the first HDR fraction than the other group. Interobserver CI did not vary significantly (0.75 ± 0.11) for HR-CTV, although a smaller CI (0.56 ± 0.21) was found for GTV.
  
  
  CONCLUSIONS
  Larger tumor regressions were observed after the first and second fractions of HDR than after all subsequent fractions. The PET-identified lymph node-positive patient group and stage III or higher tumors showed larger tumor volumes before and after EBRT than other cases.
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Sun
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Sudershan K
authors.initials: SK
authors.lastname: Bhatia
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Geraldine M
authors.initials: GM
authors.lastname: Jacobson
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Flynn
authors.affiliation: Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa. Electronic address: yusung-kim@uiowa.edu.
authors.forename: Yusung
authors.initials: Y
authors.lastname: Kim