Volumetric‐modulated arc therapy for the treatment of a large planning target volume in thoracic esophageal cancer

Abstract

Recently, volumetric‐modulated arc therapy (VMAT) has demonstrated the ability to deliver radiation dose precisely and accurately with a shorter delivery time compared to conventional intensity‐modulated fixed‐field treatment (IMRT). We applied the hypothesis of VMAT technique for the treatment of thoracic esophageal carcinoma to determine superior or equivalent conformal dose coverage for a large thoracic esophageal planning target volume (PTV) with superior or equivalent sparing of organs‐at‐risk (OARs) doses, and reduce delivery time and monitor units (MUs), in comparison with conventional fixed‐field IMRT plans. We also analyzed and compared some other important metrics of treatment planning and treatment delivery for both IMRT and VMAT techniques. These metrics include: 1) the integral dose and the volume receiving intermediate dose levels between IMRT and VMATI plans; 2) the use of 4D CT to determine the internal motion margin; and 3) evaluating the dosimetry of every plan through patient‐specific QA. These factors may impact the overall treatment plan quality and outcomes from the individual planning technique used. In this study, we also examined the significance of using two arcs vs. a single‐arc VMAT technique for PTV coverage, OARs doses, monitor units and delivery time. Thirteen patients, stage T2‐T3 N0‐N1 (TNM AJCC 7th edn.), PTV volume median 395 cc (range 281–601 cc), median age 69 years (range 53 to 85), were treated from July 2010 to June 2011 with a four‐field false(n=4false) or five‐field false(n=9false) step‐and‐shoot IMRT technique using a 6 MV beam to a prescribed dose of 50 Gy in 20 to 25 F. These patients were retrospectively replanned using single arc (normalVnormalMnormalAnormalTnormalI, 91 control points) and two arcs (normalVnormalMnormalAnormalTnormalInormalI, 182 control points). All treatment plans of the 13 study cases were evaluated using various dose‐volume metrics. These included PTV D99, PTV D95, PTV V9547.5Gyfalse(95normal%false), PTV mean dose, Dmax, PTV dose conformity (Van't Riet conformation number (CN)), mean lung dose, lung V20 and V5, liver V30, and Dmax to the spinal canal prv3mm. Also examined were the total plan monitor units (MUs) and the beam delivery time. Equivalent target coverage was observed with both VMAT single and two‐arc plans. The comparison of VMATI with fixed‐field IMRT demonstrated equivalent target coverage; statistically no significant difference were found in PTV D99 false(p=0.47false), PTV mean false(p=0.12false), PTV D95 and PTV V9547.5Gy false(95normal%false) false(p=0.38false). However, Dmax in VMATI plans was significantly lower compared to IMRT false(p=0.02false). The Van't Riet dose conformation number (CN) was also statistically in favor of VMATI plans false(p=0.04false). VMATI achieved lower lung V20 false(p=0.05false), whereas lung V5 false(p=0.35false) and mean lung dose false(p=0.62false) were not significantly different. The other OARs, including spinal canal, liver, heart, and kidneys showed no statistically significant differences bet...

Volumetric‐modulated arc therapy versus intensity‐modulated radiotherapy for large volume retroperitoneal sarcomas: A comparative analysis of dosimetric and treatment delivery parameters

“…Similar to published literature, D95 in this study was comparable between VMAT and IMRT plans ( P > 0.5); however, CI was statistically improved in favor of VMAT ( P < 0.001). The target volumes in this study, however, were significantly larger than reported by others.…”

“…Improvement in target dose delivery and reduction of dose to OARs with IMRT compared with 3D‐CRT has been established . VMAT is an improved and more efficient method of delivering IMRT as demonstrated for other tumor sites . A single feasibility study investigating the use of VMAT for treatment of RPS is reported; however, they did not perform a direct comparison of VMAT to IMRT as it has been done for other tumor sites.…”

An IMRT/VMAT Technique for Nonsmall Cell Lung Cancer

“…Several studies suggested that V 5 [11–14], V 10 [12, 14, 15], and MLD [14, 15, 17, 18] were correlated with radiation pneumonitis, although the determination of the contributors to radiation pneumonitis was challenging, since a variety of treatment/patient-related factors appeared to influence this risk.…”

“…There were several studies demonstrating that VMAT could reduce delivery time and MUs compared with IMRT [12–15]. Reduction of delivery time could decrease the possibility of the intrafraction patient motion that leads to target underdosage and/or worse OARs sparing.…”

“…However, a larger volume of lung receiving lower dose ( V 5 and V 10 ) in VMAT has been reported [10]. Dose volume histogram parameters of V 5 [11–14] and V 10 [12, 14, 15] have been showed to be the predictors of the radiation pneumonitis.…”