Dose Delivered to the Lumbosacral Plexus From High-Dose-Rate Brachytherapy for XXXX .

@entity1 @entity137 @entity5 @entity16 @entity1897
OBJECTIVE: To calculate dose delivered to the lumbosacral plexus (LSP) with cervical brachytherapy using 3-dimensional imaging, and to compare this with the position of the tandem in the pelvis using bony landmarks. We also report long-term LSP @entity137 outcomes. METHODS AND MATERIALS: Treatment planning images from 55 @entity1 treated with tandem and ring brachytherapy from October 2009 through November 2012 were reviewed. The LSP was contoured on planning computed tomographic scans to calculate dose received.Lumbosacral plexus dose was studied as a function of tandem distance from the sacrum and pubic symphysis (STratio) measured on digitally reconstructed radiographs. @entity1 and implant characteristics were included as covariates on LSP dose. Clinical follow up on LSP @entity137 was recorded. RESULTS: @entity1 were prescribed 550 to 700 cGy using computed tomography-based imaged-guided brachytherapy for 4 to 5 fractions. The maximum dose to 2 cc (D2cc) of LSP ranged from 44 to 287 cGy per implant. The median D2cc was 118 cGy, corresponding to 18% of prescription dose. @entity1 with an STratio less than 0.33 (closer to the sacrum) and at least 0.33 had median LSP doses of 138 and 98 cGy, respectively. Lumbosacral plexus dose did not change significantly with body mass index, uterus position, or @entity5 stage. Two @entity1 reported symptoms of @entity1897 , with a median follow-up of 14.7 months. CONCLUSIONS: The mean D2cc per fraction to the LSP is roughly 20% of the prescribed high dose-rate and varies with the position of the tandem from the sacrum. The dose threshold for radiation-induced @entity16 of the LSP remains undefined.
