title: Effects of interportal error on dose distribution in patients undergoing breath-holding intensity-modulated radiotherapy for pancreatic cancer: evaluation of a new treatment planning method.
abstract: In patients with pancreatic cancer, intensity-modulated radiotherapy (IMRT) under breath holding facilitates concentration of the radiation dose in the tumor, while sparing the neighboring organs at risk and minimizing interplay effects between movement of the multileaf collimator and motion of the internal structures. Although the breath-holding technique provides high interportal reproducibility of target position, dosimetric errors caused by interportal breath-holding positional error have not been reported. Here, we investigated the effects of interportal breath-holding positional errors on IMRT dose distribution by incorporating interportal positional error into the original treatment plan, using random numbers in ten patients treated for pancreatic cancer. We also developed a treatment planning technique that shortens breath-holding time without increasing dosimetric quality assurance workload. The key feature of our proposed method is performance of dose calculation using the same optimized fluence map as the original plan, after dose per fraction in the original plan was cut in half and the number of fractions was doubled. Results confirmed that interportal error had a negligible effect on dose distribution over multiple fractions. Variations in the homogeneity index and the dose delivered to 98%, 2%, and 50% of the volume for the planning target volume, and the dose delivered to 1 cc of the volume for the duodenum and stomach were ±1%, on average, in comparison with the original plan. The new treatment planning method decreased breath-holding time by 33%, and differences in dose-volume metrics between the original and the new treatment plans were within ± 1%. An additional advantage of our proposed method is that interportal errors can be better averaged out; thus, dose distribution in the proposed method may be closer to the planned dose distribution than with the original plans.
authors.affiliation: Kyoto University Hospital, Osaka University. toru1@kuhp.kyoto-u.ac.jp.
authors.forename: Toru
authors.initials: T
authors.lastname: Takakura
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.forename: Keiko
authors.initials: K
authors.lastname: Shibuya
authors.forename: Manabu
authors.initials: M
authors.lastname: Nakata
authors.forename: Akira
authors.initials: A
authors.lastname: Nakamura
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Takehiro
authors.initials: T
authors.lastname: Shiinoki
authors.forename: Kyoji
authors.initials: K
authors.lastname: Higashimura
authors.forename: Teruki
authors.initials: T
authors.lastname: Teshima
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000465:Algorithms; D062485:Breath Holding; D006801:Humans; D009038:Motion; D058958:Organs at Risk / Q000528:radiation effects; D010190:Pancreatic Neoplasms / Q000532:radiotherapy*; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061106:Radiotherapy Setup Errors / Q000517:prevention & control*; D061089:Radiotherapy, Image-Guided; D050397:Radiotherapy, Intensity-Modulated
references.citation: Cancer. 1981 Oct 15;48(8):1705-10
references.pmid: 7284971
references.citation: Int J Radiat Oncol Biol Phys. 2011 Dec 1;81(5):1328-35
references.pmid: 20934270
references.citation: J ICRU. 2010 Apr;10(1):27-40
references.pmid: 24173325
references.citation: Med Phys. 2003 Jul;30(7):1736-46
references.pmid: 12906191
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. 2011 Apr 1;79(5):1565-71
references.pmid: 20832187
references.citation: Med Phys. 2012 Jan;39(1):48-54
references.pmid: 22225274
references.citation: Int J Radiat Oncol Biol Phys. 2012 Apr 1;82(5):1619-26
references.pmid: 21477941
references.citation: Med Phys. 2001 Jan;28(1):55-66
references.pmid: 11213923
references.citation: J Clin Oncol. 1985 Mar;3(3):373-8
references.pmid: 3973648
references.citation: Med Phys. 2006 Oct;33(10):3874-900
references.pmid: 17089851
references.citation: Phys Med Biol. 2010 Jun 7;55(11):3101-13
references.pmid: 20463373
references.citation: Phys Med Biol. 2002 Jul 7;47(13):2203-20
references.pmid: 12164582
references.citation: Radiother Oncol. 2009 Aug;92(2):231-7
references.pmid: 19211167
references.citation: Int J Radiat Oncol Biol Phys. 2007 Jul 1;68(3):801-8
references.pmid: 17379445
references.citation: Med Phys. 2001 Nov;28(11):2209-19
references.pmid: 11764024
references.citation: Med Phys. 2007 Mar;34(3):923-34
references.pmid: 17441238
references.citation: Int J Radiat Oncol Biol Phys. 2004 Aug 1;59(5):1461-7
references.pmid: 15275733
references.citation: J Clin Oncol. 2010 Mar 10;28(8):1358-65
references.pmid: 20142597
references.citation: Lancet. 1969 Oct 25;2(7626):865-7
references.pmid: 4186452
references.citation: Am J Clin Oncol. 2011 Oct;34(5):460-5
references.pmid: 20881474
references.citation: J Appl Clin Med Phys. 2006 Nov 28;7(4):33-42
references.pmid: 17533350
references.citation: Int J Radiat Oncol Biol Phys. 2011 Jan 1;79(1):158-62
references.pmid: 20399035
references.citation: J Clin Oncol. 2001 Nov 15;19(22):4202-8
references.pmid: 11709563
references.citation: Int J Radiat Oncol Biol Phys. 2004 Jun 1;59(2):445-53
references.pmid: 15145161
references.citation: N Engl J Med. 1992 Feb 13;326(7):455-65
references.pmid: 1732772