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Dosimetric Impact of Four Dose Calculation Algorithms On Stereotactic Body Radiation Therapy for Lung Cancer

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T Kusunoki

T Kusunoki1*, M Kurooka2 , T Nonaka1,2 , S Yoshino3 , K Shioiri3 , S Ide3 , Y Nakayama2 , (1) Division of Radiotherapy Oncology Physics, Kanagawa Cancer Center, Yokohama, Kanagawa, (2) Department of Radiation Oncology, Kanagawa Cancer Center, Yokohama, Kanagawa, (3) Division of Radiological Technology, Kanagawa Cancer Center, Yokohama, Kanagawa


SU-I-GPD-T-599 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To evaluate the dosimetric impact of different dose calculation algorithms on stereotactic body radiation therapy (SBRT) for lung cancer.

Methods: SBRT treatment planning was performed for 56 patients with early stage lung cancer, calculated by four different dose calculation algorithms in two treatment planning systems (TPS): Acuros XB (AXB) and anisotropic analytical algorithm (AAA) in Eclipse TPS (Varian, USA), and collapsed cone algorithm (CC) and photon Monte Carlo algorithm (MC) in Monaco TPS (Elekta, USA). SBRT was delivered by 6-MV linear accelerator, and the total dose was 48 Gy in four fractions prescribed to D95 of the planning target volume (PTV). The plan calculated by AXB was obtained as the reference plan, and all plans were recalculated relative the reference plan. The dose parameters for PTV including mean dose, minimum dose, maximum dose, and conformity index (CI) were evaluated between the algorithm-generated plans. The mean CT value for the lung volume (MCVL), which was determined as the lung volume contoured by the 50% iso-dose line, was also evaluated.

Results: The averages of the minimum dose of the 56 patients were 47.1 Gy, 46.1 Gy, 47.0 Gy and 45.2 Gy for AXB, MC, AAA and CC, respectively, and the difference between AXB and CC was significant. There was a trend that the difference of the minimum dose calculated by AAA and CC compared with AXB was greater in patients with low MCVL. In addition, the average of mean dose was lowest when calculated by CC (50.3 Gy), and consequently the mean CI was significantly poor when calculated by AAA and CC (0.57 and 0.55).

Conclusion: Our results suggested that, in SBRT for lung cancer, the dose should be carefully evaluated when the plan was calculated by AAA or CC, especially in patients with low MCVL.

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