title: Three-dimensional dose accumulation in pseudo-split-field IMRT and brachytherapy for locally advanced cervical cancer.
abstract: OBJECTIVE
  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
  Thirty-three patients treated with split-field-IMRT to 45.0-51.2 Gy in 1.6-1.8 Gy per fraction to the elective pelvic lymph nodes and to 20 Gy to the central pelvis region were included in this study. Patients received six weekly fractions of high-dose rate BT to 6.5-7.3 Gy per fraction. A dose tracker software was developed to compute the 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 ± 26.5 Gy and D2cc was 99.6 ± 13.9 Gy, 67.4 ± 12.2 Gy, 75.0 ± 10.1 Gy, for bladder, rectum, and sigmoid, respectively. The uncertainties induced by organ deformation were estimated to be -1 ± 4 Gy, -3 ± 5 Gy, 2 ± 3 Gy, and -3 ± 5 Gy 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.
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO. Electronic address: bsun@radonc.wustl.edu.
authors.forename: Baozhou
authors.initials: B
authors.lastname: Sun
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO.
authors.forename: Deshan
authors.initials: D
authors.lastname: Yang
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO.
authors.forename: Jackie
authors.initials: J
authors.lastname: Esthappan
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO.
authors.forename: Jose
authors.initials: J
authors.lastname: Garcia-Ramirez
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO.
authors.forename: Samantha
authors.initials: S
authors.lastname: Price
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO.
authors.forename: Sasa
authors.initials: S
authors.lastname: Mutic
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO.
authors.forename: Julie K
authors.initials: JK
authors.lastname: Schwarz
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO.
authors.forename: Perry W
authors.initials: PW
authors.lastname: Grigsby
authors.affiliation: Department of Radiation Oncology, Washington University Saint Louis, MO.
authors.forename: Kari
authors.initials: K
authors.lastname: Tanderup
mesh_terms: D000328:Adult; D001918:Brachytherapy / Q000379:methods*; D012809:Colon, Sigmoid / Q000528:radiation effects; D019583:Dose Fractionation, Radiation; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
keywords: Cervical cancer; Dose accumulation; Image-guided brachytherapy