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Stereotactic radiation treatment planning with volumetric modulated arc therapy: Impact of duodenal sparing on pancreatic tumor coverage.
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| Zeitschriftentitel: | Journal of Clinical Oncology |
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| Personen und Körperschaften: | , , , , , , , , , |
| In: | Journal of Clinical Oncology, 29, 2011, 4_suppl, S. 301-301 |
| Format: | E-Article |
| Sprache: | Englisch |
| veröffentlicht: |
American Society of Clinical Oncology (ASCO)
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| Schlagwörter: |
| Zusammenfassung: | <jats:p> 301 </jats:p><jats:p> Background: Volumetric modulated arc therapy (VMAT) allows for intensity-modulated radiation delivery with faster treatment times and fewer delivered monitor units (MU). The dose-limiting structure for pancreatic stereotactic body radiation therapy (SBRT) is the duodenum. We evaluate VMAT dose distribution, delivery times, and the effect of duodenal sparing (DS) for pancreas SBRT. </jats:p><jats:p> Methods: Plans of 15 patients with unresectable pancreatic cancer (14 head/1 tail) were selected. VMAT treatment planning with the “SmartArc” function of Pinnacle v. 8.9 was used to plan one fraction of 25 Gy to the PTV (gross tumor + 2 mm expansion) normalized to the 80% isodose line. Two VMAT SBRT plans were conducted for each case; the first did not attempt to spare the duodenum (non DS) while the second did (DS). Constraints were stomach/duodenum any point max <30 Gy (for DS plan), liver D<jats:sub>50</jats:sub> < 5 Gy, ipsilateral kidney D<jats:sub>25</jats:sub> < 5 Gy, cord D<jats:sub>max</jats:sub> < 5 Gy and stomach D<jats:sub>4</jats:sub> < 22.5 Gy. </jats:p><jats:p> Results: Gross tumor volume ranged from 58.4cm<jats:sup>3</jats:sup> to 320.3 cm<jats:sup>3</jats:sup>. The average overlap volume between PTV and the duodenum was 8.4 cm<jats:sup>3</jats:sup>. In 10/15 non-DS plans, the duodenal D<jats:sub>max</jats:sub> exceeded 30 Gy. With DS optimization, only 1/15 plans exceeded the 30 Gy threshold. These differences were statistically significant (p<0.001). Typical MU and delivery times, as calculated by the planning software, were 5494 MU and 775 secs vs. 5296 MU and 703 secs for the DS and non-DS plans, respectively. The difference in delivery times was significant (p=0.01), but amounted to only 1.2 min on average. The average duodenal D<jats:sub>max</jats:sub> for non-DS plans was 30.4Gy, D<jats:sub>4%</jats:sub> was 23.4 Gy. With DS, the average D<jats:sub>max</jats:sub> was reduced to 28.1Gy and D<jats:sub>4%</jats:sub> to <19.7 Gy (p<0.001). As expected, VMAT plans with greater overlap between the duodenum and PTV had a higher duodenal D<jats:sub>max</jats:sub>. </jats:p><jats:p> Conclusions: This study demonstrates the feasibility of VMAT for high-dose SBRT treatment of pancreatic cancer incorporating constraints to limit the dose to the duodenum. Future studies will evaluate whether VMAT with fractionated SBRT results in improved duodenal sparing more efficiently than traditional IMRT. </jats:p><jats:p> No significant financial relationships to disclose. </jats:p> |
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| Umfang: | 301-301 |
| ISSN: |
0732-183X
1527-7755 |
| DOI: | 10.1200/jco.2011.29.4_suppl.301 |