Abstract
BackgroundTo evaluate the dosimetric and biological benefits of the fixed-jaw (FJ) intensity-modulated radiation therapy (IMRT) technique for patients with T-shaped esophageal cancer.MethodsFJ IMRT plans were generated for thirty-five patients and compared with jaw tracking (JT) IMRT, static jaw (SJ) IMRT and JT volumetric modulated arc therapy (VMAT). Dosimetric parameters, tumor control probability (TCP) and normal tissue complication probability (NTCP), monitor units (MUs), delivery time and gamma passing rate, as a measure of dosimetric verification, were compared. The correlation between the length of PTV-C below the upper boundary of lung tissue (PTV-Cinferior) and dosimetric parameters and NTCP of the lung tissue were analyzed.ResultsThe homogeneity and conformity of the target in the four plans were basically equivalent. When compared to the JT IMRT and SJ IMRT plans, FJ IMRT plan led to a statistically significant improvement in the NTCP and low-middle dosimetric parameters of the lung, and the improvement had a moderately positive correlation with the length of PTV-Cinferior, with a correlation coefficient ranging from 0.523 to 0.797; the FJ IMRT plan exhibited better lung sparing in low-dose volumes than the JT VMAT plan. The FJ IMRT plan had similar MUs (888 ± 99) and delivery times (516.1 ± 54.7 s) as the JT IMRT plan (937 ± 194, 522 ± 5.6 s) but higher than SJ IMRT (713 ± 137, 488.8 ± 45.2 s) and JT VMAT plan (517 ± 59, 263.7 ± 43.3 s).ConclusionsThe FJ IMRT technique is superior in reducing the low-dose volumes of lung tissues for patients with T-shaped esophageal cancer.
Highlights
To evaluate the dosimetric and biological benefits of the fixed-jaw (FJ) intensity-modulated radiation therapy (IMRT) technique for patients with T-shaped esophageal cancer
This study aimed to explore the feasibility of the fixedjaw IMRT technique for T-shaped esophageal cancer in comparison with the jaw tracking IMRT, static jaw IMRT and jaw tracking volumetric modulated arc therapy (VMAT) techniques in terms of dosimetry parameters, tumor control probability (TCP) and normal tissue complication probability (NTCP) values
The results showed that the dosimetric parameters of the FJ IMRT technique could meet the clinical requirements like the other three techniques; the D2, D98, conformity and homogeneity for the planning target volume (PTV)-G and PTV-C with the FJ IMRT plan were not significantly different from those of the jaw tracking (JT) IMRT and static jaw (SJ) IMRT plans, and this was consistent with the study from Wang et al [16] and Song et al [18]
Summary
Patient characteristics Thirty-five patients with histologically or cytologically confirmed T-shaped esophageal cancer with different lengths of target below the upper boundary of lung tissue who were treated with radiotherapy between January 2017 and May 2018 were selected for this study. PTV, Planning target volume; PTV-Cinferior, the part of the PTV-C below the upper boundary of lung tissue slice thickness of 5 mm. Contouring the targets and OARs The target volumes and OARs of each patient were delineated by a qualified physician with more than 10 years of experience in clinical radiation oncology. The clinical target volume (CTV) was defined as the GTV plus the bilateral supraclavicular lymph nodes and upper-middle mediastinal lymph nodes. The jaw tracking function on Pinnacle was selected, and the plans automatically set the positions of each pair of jaws to reduce radiation leakage and transmission. For the SJ IMRT plan, beam parameter settings identical to the corresponding JT IMRT plans were employed
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