Proof of principle: Applicator-guided stereotactic IMRT boost in combination with 3D MRI-based brachytherapy in locally advanced cervical cancer

Brachytherapy. Jul-Aug 2014;13(4):361-8. doi: 10.1016/j.brachy.2014.02.003. Epub 2014 Mar 18.

Abstract

Purpose: 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 and materials: 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.

Keywords: Applicator-guidance; Brachytherapy; Cervical cancer; IMRT boost; MRI-guidance.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Brachytherapy / methods*
  • Carcinoma, Squamous Cell / pathology
  • Carcinoma, Squamous Cell / radiotherapy*
  • Colon, Sigmoid
  • Dose Fractionation, Radiation
  • Feasibility Studies
  • Female
  • Follow-Up Studies
  • Humans
  • Imaging, Three-Dimensional*
  • Magnetic Resonance Imaging / methods*
  • Middle Aged
  • Neoplasm Staging
  • Organs at Risk
  • Radiotherapy Dosage
  • Radiotherapy Planning, Computer-Assisted / methods
  • Radiotherapy, Intensity-Modulated / methods*
  • Rectum
  • Treatment Outcome
  • Urinary Bladder
  • Uterine Cervical Neoplasms / pathology
  • Uterine Cervical Neoplasms / radiotherapy*