title: Proof of principle: Applicator-guided stereotactic IMRT boost in combination with 3D MRI-based brachytherapy in locally advanced cervical cancer.
abstract: OBJECTIVE
  To describe a new technique involving high-precision stereotactic intensity-modulated radiation therapy (IMRT) boost in combination with intracavitary-interstitial (IC-IS) brachytherapy (BT) in cervical tumors that cannot be sufficiently covered by IC-IS-BT due to extensive residual disease and/or difficult topography at the time of BT.
  
  
  METHODS
  Three patients with stage IIIB-IVA cervical cancer had significant residual disease at the time of BT. MRI-guided IC-IS-BT (pulsed-dose rate) was combined with a stereotactic IMRT boost guided according to the BT applicator in situ, using cone beam CT. The planning aim dose (total external beam radiotherapy and BT) for the high-risk clinical target volume (HR-CTV) was D90 >70-85 Gy, whereas constraints for organs at risk were D2cm3 <70 Gy for rectum, sigmoid, and bowel and <90 Gy for bladder in terms of equivalent total dose in 2 Gy fractions. An IMRT boost adapted to the BT dose distribution was optimized to target the regions poorly covered by BT.
  
  
  RESULTS
  HR-CTV doses of D90 >81 Gy were obtained in the central HR-CTV and D90 >69 Gy in the distal regions of HR-CTV. Image-guided set up of the IMRT boost with the applicator in situ was feasible. The dose plans were robust to intra-fraction uncertainties of 3 mm. Local control with acceptable morbidity was obtained at a followup of 3, 2.5, and 1 year, respectively.
  
  
  CONCLUSIONS
  The combination of MRI-guided BT with an applicator-guided stereotactic IMRT boost is feasible. This technique seems to be useful in the few cases where HR-CTV coverage cannot be obtained even with IS-IC-BT.
authors.affiliation: Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark. Electronic address: mariasse@rm.dk.
authors.forename: Marianne S
authors.initials: MS
authors.lastname: Assenholt
authors.affiliation: Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Anne
authors.initials: A
authors.lastname: Vestergaard
authors.affiliation: Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Jesper F
authors.initials: JF
authors.lastname: Kallehauge
authors.affiliation: Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Sandy
authors.initials: S
authors.lastname: Mohamed
authors.affiliation: Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Søren K
authors.initials: SK
authors.lastname: Nielsen
authors.affiliation: Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Jørgen B
authors.initials: JB
authors.lastname: Petersen
authors.affiliation: Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Fokdal
authors.affiliation: Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Lindegaard
authors.affiliation: Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark; Department of Oncology, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.
authors.forename: Kari
authors.initials: K
authors.lastname: Tanderup
mesh_terms: D000328:Adult; D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy*; D012809:Colon, Sigmoid; D019583:Dose Fractionation, Radiation; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D009367:Neoplasm Staging; D058958:Organs at Risk; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum; D016896:Treatment Outcome; D001743:Urinary Bladder; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*
keywords: Applicator-guidance; Brachytherapy; Cervical cancer; IMRT boost; MRI-guidance