Abstract

Purpose: Dose accumulation of split-field external beam radiotherapy (EBRT) and brachytherapy (BT) is challenging because of significant EBRT and BT dose gradients in the central pelvic region. We developed a method to determine biologically effective dose parameters for combined split-field intensity-modulated radiation therapy (IMRT) and image-guided BT in locally advanced cervical cancer. Methods and Materials: Thirty-three patients treated with split-field-IMRT to 45.0-51.2Gy in 1.6-1.8Gy per fraction to the elective pelvic lymph nodes and to 20Gy to the central pelvis region were included in this study. Patients received six weekly fractions ofhigh-dose rate BT to 6.5-7.3Gy per fraction. A dose tracker software was developed to computethe equivalent dose in 2-Gy fractions (EQD2) to gross tumor volume (GTV), organs-at-risk and point A. Total dose-volume histogram parameters were computed on the 3D combined EQD2 dose based on rigid image registration. The dose accumulation uncertainty introduced by organ deformations between IMRT and BT was evaluated. Results: According to International Commission on Radiation Unit and Measurement and GEC European Society for Therapeutic Radiology and Oncology recommendations, D98, D90, D50, and D2cm3 EQD2 dose-volume histogram parameters were computed. GTV D98 was 84.0±26.5Gy and D2cc was 99.6±13.9Gy, 67.4±12.2Gy, 75.0±10.1Gy, for bladder, rectum, and sigmoid, respectively. The uncertainties induced by organ deformation were estimated to be -1±4Gy, -3±5Gy, 2±3Gy, and -3±5Gy for bladder, rectum, sigmoid, and GTV, respectively. Conclusions: It is feasible to perform 3D EQD2 dose accumulation to assess high and intermediate dose regions for combined split-field IMRT and BT.

Original languageEnglish
Pages (from-to)481-489
Number of pages9
JournalBrachytherapy
Volume14
Issue number4
DOIs
StatePublished - Jul 1 2015

Keywords

  • Cervical cancer
  • Dose accumulation
  • Image-guided brachytherapy

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