title: 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.
abstract: 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 25Gy in 1 fraction were generated for 15 patients with LAPC. DS plans were constrained to duodenal Dmax of<30Gy at any point. VMAT used 1 360° coplanar arc with 4° spacing between control points, whereas IMRT used 9 coplanar beams with fixed gantry positions at 40° 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 Dmean, Dmax, D1cc, D4%, and V20Gy compared with NS plans (all p≤0.002). DS constraints compromised target coverage for IMRT as demonstrated by reduced V95% (p = 0.01) and Dmean (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.
authors.affiliation: Department of Radiation Oncology & Molecular Radiation Sciences, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins Hospital, 401 N. Broadway, Baltimore, MD 21231, USA.
authors.forename: Rachit
authors.initials: R
authors.lastname: Kumar
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Wild
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ziegler
authors.forename: Ted K
authors.initials: TK
authors.lastname: Hooker
authors.forename: Samson D
authors.initials: SD
authors.lastname: Dah
authors.forename: Phuoc T
authors.initials: PT
authors.lastname: Tran
authors.forename: Jun
authors.initials: J
authors.lastname: Kang
authors.forename: Koren
authors.initials: K
authors.lastname: Smith
authors.forename: Jing
authors.initials: J
authors.lastname: Zeng
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Pawlik
authors.forename: Erik
authors.initials: E
authors.lastname: Tryggestad
authors.forename: Eric
authors.initials: E
authors.lastname: Ford
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Herman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004386:Duodenum / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000601:surgery*; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
keywords: Duodenal sparing; IMRT; Pancreatic cancer; VMAT
references.citation: J Clin Oncol. 2009 May 1;27(13):2269-77
references.pmid: 19307501
references.citation: Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3):935-42
references.pmid: 20044214
references.citation: Radiother Oncol. 2009 Jul;92(1):118-24
references.pmid: 19181409
references.citation: J Clin Oncol. 2005 Jul 10;23(20):4538-44
references.pmid: 16002845
references.citation: Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3 Suppl):S101-7
references.pmid: 20171503
references.citation: Radiat Oncol. 2010 Oct 13;5:92
references.pmid: 20942958
references.citation: Radiat Oncol. 2011 Oct 31;6:147
references.pmid: 22040762
references.citation: Med Dosim. 2002 Summer;27(2):121-9
references.pmid: 12074463
references.citation: Int J Radiat Oncol Biol Phys. 2012 Jul 1;83(3):901-8
references.pmid: 22483737
references.citation: Med Dosim. 2012 Autumn;37(3):271-5
references.pmid: 22189026
references.citation: Radiother Oncol. 2009 Jul;92(1):111-7
references.pmid: 19157609
references.citation: Strahlenther Onkol. 2010 Jul;186(7):382-7
references.pmid: 20582394
references.citation: Cancer. 2009 Feb 1;115(3):665-72
references.pmid: 19117351
references.citation: CA Cancer J Clin. 2012 Jan-Feb;62(1):10-29
references.pmid: 22237781
references.citation: Med Dosim. 2011 Autumn;36(3):317-20
references.pmid: 20846850
references.citation: Int J Radiat Oncol Biol Phys. 2010 Dec 1;78(5):1420-6
references.pmid: 20399033
references.citation: Radiother Oncol. 2008 Nov;89(2):180-91
references.pmid: 18692929
references.citation: Strahlenther Onkol. 2009 Sep;185(9):557-66
references.pmid: 19756421
references.citation: Int J Radiat Oncol Biol Phys. 2004 Jun 1;59(2):454-9
references.pmid: 15145162
references.citation: Int J Radiat Oncol Biol Phys. 2006 May 1;65(1):274-83
references.pmid: 16618582
references.citation: Int J Radiat Oncol Biol Phys. 2004 Jun 1;59(2):445-53
references.pmid: 15145161
references.citation: Phys Med Biol. 2009 Jan 7;54(1):N9-20
references.pmid: 19075362