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Comparison of Five Types of Adaptive X-Ray Treatment Planning Technique for Locally Advanced Non-Small Cell Lung Cancer

M Saito*, T Komiyama, K Marino, S Aoki, Y Maehata, M Matsuda, T Akita, H Suzuki, K Ueda, H Onishi,

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: purpose of this study was to compare five types of adaptive X-ray treatment planning technique for locally advanced non-small cell lung cancer (LANSCLC) patient.

Methods: types of treatment plan (f-3DCRT: forward planned 3DCRT (2-6 fixed beams), i-3DCRT: inverse planned 3DCRT (8 fixed beams with optimizing gantry angle, collimator angle, beam shape, and beam weight), VMAT: volumetric modulated arc therapy (1-3 partial arcs), 3DCRT+VMAT: initial 3DCRT and boost VMAT, and Hybrid: hybrid of 2 fixed IMRT beams and VMAT) were created for 13 stage III NSCLC patients. The target prescription dose was 60Gy/30Fr (initial plan: 40Gy/20Fr, and boost plan: 20Gy/10Fr). The two plan doses were combined into accumulated dose using deformable image registration, because the initial plan and the boost plan had used different CT images to adapt the change of patient geometry and tumor shrinkage. In this study, the accumulated doses were compared among all treatment techniques.

Results: average conformity index (CI) of the planning target volume (PTV) for all patients were 0.34±0.10, 0.57±0.10, 0.86±0.08 0.61±0.12, and 0.83±0.11 for f-3DCRT, i-3DCRT, VMAT, 3DCRT+VMAT, and Hybrid respectively. In the same manner, lung volume receiving >5 Gy (V5Gy) were 34.9±14.5%, 39.8±10.6%, 48.0±17.4%, 36.9±14.9%, and 43.1±15.4% and lung volume receiving >20 Gy (V20Gy) were 21.0±10.6%, 20.9±6.45%, 19.5±7.4%, 20.0±10.0%, and 17.7±7.86%. There was significant improvement about CI and V20 for VMAT and Hybrid compared with other techniques (p<0.05). On the other hands, 3DCRT techniques provided lower V5 and monitor unit (MU) than VMAT (average MU of initial plan: 255±13.2 (f-3DCRT) vs. 281±10.5 (i-3DCRT) vs. 655±159 (VMAT), p<0.05).

Conclusion: IMRT/VMAT hybrid beam might be best choice for improvement of dose distribution. On the other hands, some 3DCRT combined methods could provide some benefit for lowest monitor unit and lung V5Gy.

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