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A Novel Hybrid Planning Strategy for Stereotactic Body Radiation Therapy of Early Stage Non-Small-Cell Lung Cancer

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H Liu

H Liu1*, T Hayes2 , Q Shang3 , K Pearman4 , B Sintay5 , J Maurer6 , D Wiant7 , (1) Cone Health Cancer Center, Greensboro, NC, (2) Cone Health Cancer Center, Greensboro, NC, (3) ,Greensboro, NC, (4) Cone health cancer center, Greensboro, NC, (5) Cone Health, Summerfield, NC, (6) Cone Health Cancer Center, Greensboro, NC, (7) Cone Health Cancer Center, Greensboro, NC


SU-I-GPD-T-608 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Dynamic conformal arc (DCA) therapy has an advantage over volumetric modulated arc therapy (VMAT) in terms of the MLC motion, positioning error, and delivery efficiency. However, VMAT is the treatment choice when critical organ sparing becomes important because of the increased ability for dose shaping. In this study we developed a hybrid planning strategy to incorporate DCA component into the VMAT planning.

Methods: Ten lung SBRT patients were retrospectively reviewed (5 received 54Gy in 3 fractions and 5 received 50Gy in 5 fractions). Four planning techniques were simulated: DCA, Hybrid-DCA (2/3 of the dose from DCA beams), Hybrid-VMAT (2/3 of the dose from VMAT beams) and VMAT. All plans had at least 95% PTV coverage. Conformity index (CI) for the PTV, V20 for lung, V30 for chest wall, and maximum dose to all other critical organs were computed. Modulation complexity score (MCS) was calculated (large MCS = less plan complexity). The correlation of MCS, total MU, used and gamma passing rates were studied.

Results: For 4 out of 10 patients, the DCA technique did not result in acceptable plan quality due to target location. Hybrid-DCA produced one unacceptable plan, and Hybrid-VMAT and VMAT produced no unacceptable plans. The CI improved with increasing VMAT usage, as did the dose sparing to critical structures. The average total MUs used were 2661, 3241, 3771 and 4302 for DCA, Hybrid-DCA, Hybrid-VMAT and VMAT, respectively, indicating a significant improvement in the delivery efficiency with increasing use of DCA. Gamma passing rates and MCS increased with more DCA contributions. The MCS showed a strong correlation with the gamma passing rate, and an inverse correlation with the total MU used.

Conclusion: Both hybrid techniques offer comparable dosimetry to full VMAT, while minimizing the MLC complexity.

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