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Dosimetric Benefit of Adaptive Re-Planning in Lung Cancer Stereotactic Body Radiotherapy (SBRT)

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J Jia

J Jia1*, Z Tian2 , X Gu3 , H Yan4 , X Jia5 , S Jiang6 , (1) University of Science and Technology of China, Hefei, Anhui, (2) UT Southwestern Medical Ctr at Dallas, Dallas, TX, (3) UT Southwestern Medical Center, Dallas, TX, (4) UT Southwestern Medical Center, Dallas, TX, (5) The University of Texas Southwestern Medical Ctr, Dallas, TX, (6) UT Southwestern Medical Center, Dallas, TX


SU-E-J-52 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:To investigate the dosimetric benefit of adaptive re-planning for lung stereotactic body radiotherapy(SBRT).

Methods:Five lung cancer patients with SBRT treatment were retrospectively investigated. Our in-house supercomputing online re-planning environment (SCORE) was used to realize the re-planning process. First a deformable image registration was carried out to transfer contours from treatment planning CT to each treatment CBCT. Then an automatic re-planning using original plan DVH guided fluence-map optimization is performed to get a new plan for the up-to-date patient geometry. We compared the re-optimized plan to the original plan projected on the up-to-date patient geometry in critical dosimetric parameters, such as PTV coverage, spinal cord maximum and volumetric constraint dose, esophagus maximum and volumetric constraint dose.

Results:The average volume of PTV covered by prescription dose for all patients was improved by 7.56% after the adaptive re-planning. The volume of the spinal cord receiving 14.5Gy and 23Gy (V14.5, V23) decreased by 1.48% and 0.68%, respectively. For the esophagus, the volume receiving 19.5Gy (V19.5) reduced by 1.37%. Meanwhile, the maximum dose dropped off by 2.87% for spinal cord and 4.80% for esophagus.

Conclusion:Our experimental results demonstrate that adaptive re-planning for lung SBRT has the potential to minimize the dosimetric effect of inter-fraction deformation and thus improve target coverage while reducing the risk of toxicity to nearby normal tissues.

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