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KMID : 1038720200310040179
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Progress in Medical Physics
2020 Volume.31 No. 4 p.179 ~ p.188
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Dosimetric Comparison of Noncoplanar and Coplanar Volumetric Modulated Arc Therapy Plans for Esophageal Cancer
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Park So-Yeon
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Abstract
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Purpose: We compared noncoplanar volumetric modulated arc therapy (ncVMAT) plans to coplanar VMAT (cVMAT) plans by evaluating the dosimetric quality of each for esophageal cancer.
Methods: Twenty patients treated for esophageal cancer with the cVMAT technique were retrospectively selected. The cVMAT plans consisted of three coplanar full arc beams. The ncVMAT plans consisted of two coplanar full arc beams and one noncoplanar partial arc beam ranging from 45° to 315° with a couch rotation angle of 315°±5°. For dosimetric evaluation, the dose-volumetric (DV) parameters of the planning target volume (PTV) and organs at risk (OARs) were calculated for all VMAT plans.
Results: No clinically noticeable differences between the cVMAT and ncVMAT plans were observed in the DV parameters of the PTV. For the lungs, the VM13 Gy and mean dose for ncVMAT plans were smaller than those for cVMAT plans, showing statistically significant differences. For the heart, the values of the maximum dose for cVMAT and ncVMAT plans were 53.8±2.9 and 50.9±3.3 Gy, respectively (P=0.004). For the spinal cord, the values of the maximum dose for cVMAT and ncVMAT plans were 37.1±5.1 and 34.7±5.7 Gy, respectively (P<0.001).
Conclusions: The use of ncVMAT plans provides better PTV coverage and sparing of OARs compared to that of cVMAT plans for long, tube-like esophageal cancer. For esophageal cancer, the ncVMAT plans showed a more favorable plan quality than the cVMAT plans.
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KEYWORD
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Dosimetric evaluation, Noncoplanar, Volumetric modulated arc therapy, Esophageal cancer
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