Stereotactic body radiation therapy planning with duodenal sparing using Volumetric-modulated arc therapy vs intensity-modulated radiation therapy in locally advanced pancreatic cancer: A dosimetric analysis

作者:Kumar Rachit; Wild Aaron T; Ziegler Mark A; Hooker Ted K; Dah Samson D; Tran Phuoc T; Kang Jun; Smith Koren; Zeng Jing; Pawlik Timothy M; Tryggestad Erik; Ford Eric; Herman Joseph M*
来源:Medical Dosimetry, 2013, 38(3): 243-250.
DOI:10.1016/j.meddos.2013.02.003

摘要

Stereotactic body radiation therapy (SBRT) achieves excellent local control for locally advanced pancreatic cancer (LAPC), but may increase late duodenal toxicity. Volumetric-modulated arc therapy (VMAT) delivers intensity-modulated radiation therapy (IMRT) with a rotating gantry rather than multiple fixed beams. This study dosimetrically evaluates the feasibility of implementing duodenal constraints for SBRT using VMAT vs IMRT. Non-duodenal sparing (NS) and duodenal-sparing (DS) VMAT and IMRT plans delivering 25 Gy in 1 fraction were generated for 15 patients with LAPC. DS plans were constrained to duodenal D-max of <30 Gy at any point. VMAT used 1 360 degrees coplanar arc with 4 degrees spacing between control points, whereas IMRT used 9 coplanar beams with fixed gantry positions at 40 degrees angles. Dosimetric parameters for target volumes and organs at risk were compared for DS planning vs NS planning and VMAT vs IMRT using paired-sample Wilcoxon signed rank tests. Both DS VMAT and DS IMRT achieved significantly reduced duodenal D-mean, D-max, D-1cc, D-4%, and V-20 (Gy) compared with NS plans (all p <= 0.002). DS constraints compromised target coverage for IMRT as demonstrated by reduced V-95% (p = 0.01) and D-mean (p = 0.02), but not for VMAT. DS constraints resulted in increased dose to right kidney, spinal cord, stomach, and liver for VMAT. Direct comparison of DS VMAT and DS IMRT revealed that VMAT was superior in sparing the left kidney (p < 0.001) and the spinal cord (p < 0.001), whereas IMRT was superior in sparing the stomach (p = 0.05) and the liver (p = 0.003). DS VMAT required 21% fewer monitor units (p < 0.001) and delivered treatment 2.4 minutes faster (p < 0.001) than DS IMRT. Implementing DS constraints during SBRT planning for LAPC can significantly reduce duodenal point or volumetric dose parameters for both VMAT and IMRT. The primary consequence of implementing DS constraints for VMAT is increased dose to other organs at risk, whereas for IMRT it is compromised target coverage. These findings suggest clinical situations where each technique may be most useful if DS constraints are to be employed.

  • 出版日期2013