title: Lumbosacral plexus delineation, dose distribution, and its correlation with radiation-induced lumbosacral plexopathy in cervical cancer patients.
abstract: BACKGROUND
  To evaluate the dose distribution to the lumbosacral plexus (LSP) and its correlation with radiation-induced lumbosacral plexopathy (RILSP) in patients with cervical cancer treated with intensity-modulated radiotherapy (IMRT) and high-dose-rate brachytherapy.
  
  
  METHODS
  After meeting eligibility criteria, 50 patients with cervical cancer were selected who were treated with IMRT and high-dose-rate brachytherapy, and the LSP was contoured. Mean volume; percentages of LSP volume absorbing 40, 50, 55, and 60 Gy (V30, V40, V50, V55, and V60) and point doses (P1, P2, P3, P4, P5, P6, P7, P8, P9, and P10); and RILSP incidence were calculated.
  
  
  RESULTS
  At 60 months of follow-up, four patients (8%) were found to have grade 2/3 RILSP. The mean maximal LSP dose in patients with RILSP was 59.6 Gy compared with 53.9 Gy in patients without RILSP (control; P=0.04). The mean values of V40, V50, V55, and V60 in patients with RILSP versus control were 61.8% versus 52.8%, 44.4% versus 27.7%, 8.0% versus 0.3% and 1.8% versus 0%, respectively (P=0.01, 0.001, 0.001, and 0.001, respectively).
  
  
  CONCLUSIONS
  The delineation of the LSP during IMRT planning may reduce the risk for RILSP. The mean values of V40, V50, V55, and V60 for LSP should be less than 55%, 30%, 5%, and 0.5%, respectively; however, further studies are warranted.
authors.affiliation: Radiation Oncology, Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia.
authors.forename: Mutahir
authors.initials: M
authors.lastname: Tunio
authors.affiliation: Radiation Oncology, Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia.
authors.forename: Mushabbab
authors.initials: M
authors.lastname: Al Asiri
authors.affiliation: National Cancer Institute, Cairo University, Cairo, Egypt.
authors.forename: Yasser
authors.initials: Y
authors.lastname: Bayoumi
authors.affiliation: Radiation Oncology, Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia.
authors.forename: Ali
authors.initials: A
authors.lastname: Abdullah O Balbaid
authors.affiliation: Neurology, Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia.
authors.forename: Majid
authors.initials: M
authors.lastname: AlHameed
authors.affiliation: Radiation Oncology, Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia.
authors.forename: Stanciu Laura
authors.initials: SL
authors.lastname: Gabriela
authors.affiliation: Radiation Oncology, Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Amir O Ali
keywords: cervical cancer; dosimetric analysis; intensity-modulated radiation therapy; lumbosacral plexus delineation; radiation-induced lumbosacral plexopathy