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      Planning analysis for locally advanced lung cancer: dosimetric and efficiency comparisons between intensity-modulated radiotherapy (IMRT), single-arc/partial-arc volumetric modulated arc therapy (SA/PA-VMAT)


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          To analyze the differences between the intensity-modulated radiotherapy (IMRT), single/partial-arc volumetric modulated arc therapy (SA/PA-VMAT) techniques in treatment planning for locally advanced lung cancer.

          Materials and methods

          12 patients were retrospectively studied. In each patient's case, several parameters were analyzed based on the dose-volume histograms (DVH) of the IMRT, SA/PA-VMAT plans respectively. Also, each plan was delivered to a phantom for time comparison.


          The SA-VMAT plans showed the superior target dose coverage, although the minimum/mean/maximum doses to the target were similar. For the total and contralateral lungs, the higher V 5/10, lower V 20/30 and mean lung dose (MLD) were observed in the SA/PA-VMAT plans ( p < 0.05, respectively). The PA-VMAT technique improves the dose sparing (V 20, V 30 and MLD) of the controlateral lung more notably, comparing to those parameters of the IMRT and SA-VMAT plans respectively. The delivered monitor units (MUs) and treatment times were reduced significantly with VMAT plans, especially PA-VMAT plans (for MUs: mean 458.3 vs. 439.2 vs. 435.7 MUs, p < 0.05 and for treatment time: mean 13.7 vs. 10.6 vs. 6.4 minutes, p < 0.01).


          The SA-VMAT technique achieves highly conformal dose distribution to the target. Comparing to the IMRT plans, the higher V 5/10, lower V 20/30 and MLD were observed in the total and contralateral lungs in the VMAT plans, especially in the PA-VMAT plans. The SA/PA-VMAT plans also reduced treatment time with more efficient dose delivering. But the clinical benefit of the VMAT technique for locally advanced lung cancer needs further investigations.

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          Most cited references19

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          Volumetric modulated arc therapy: IMRT in a single gantry arc.

          In this work a novel plan optimization platform is presented where treatment is delivered efficiently and accurately in a single dynamically modulated arc. Improvements in patient care achieved through image-guided positioning and plan adaptation have resulted in an increase in overall treatment times. Intensity-modulated radiation therapy (IMRT) has also increased treatment time by requiring a larger number of beam directions, increased monitor units (MU), and, in the case of tomotherapy, a slice-by-slice delivery. In order to maintain a similar level of patient throughput it will be necessary to increase the efficiency of treatment delivery. The solution proposed here is a novel aperture-based algorithm for treatment plan optimization where dose is delivered during a single gantry arc of up to 360 deg. The technique is similar to tomotherapy in that a full 360 deg of beam directions are available for optimization but is fundamentally different in that the entire dose volume is delivered in a single source rotation. The new technique is referred to as volumetric modulated arc therapy (VMAT). Multileaf collimator (MLC) leaf motion and number of MU per degree of gantry rotation is restricted during the optimization so that gantry rotation speed, leaf translation speed, and dose rate maxima do not excessively limit the delivery efficiency. During planning, investigators model continuous gantry motion by a coarse sampling of static gantry positions and fluence maps or MLC aperture shapes. The technique presented here is unique in that gantry and MLC position sampling is progressively increased throughout the optimization. Using the full gantry range will theoretically provide increased flexibility in generating highly conformal treatment plans. In practice, the additional flexibility is somewhat negated by the additional constraints placed on the amount of MLC leaf motion between gantry samples. A series of studies are performed that characterize the relationship between gantry and MLC sampling, dose modeling accuracy, and optimization time. Results show that gantry angle and MLC sample spacing as low as 1 deg and 0.5 cm, respectively, is desirable for accurate dose modeling. It is also shown that reducing the sample spacing dramatically reduces the ability of the optimization to arrive at a solution. The competing benefits of having small and large sample spacing are mutually realized using the progressive sampling technique described here. Preliminary results show that plans generated with VMAT optimization exhibit dose distributions equivalent or superior to static gantry IMRT. Timing studies have shown that the VMAT technique is well suited for on-line verification and adaptation with delivery times that are reduced to approximately 1.5-3 min for a 200 cGy fraction.
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            Analysis of clinical and dosimetric factors associated with treatment-related pneumonitis (TRP) in patients with non-small-cell lung cancer (NSCLC) treated with concurrent chemotherapy and three-dimensional conformal radiotherapy (3D-CRT).

            To investigate factors associated with treatment-related pneumonitis in non-small-cell lung cancer patients treated with concurrent chemoradiotherapy. We retrospectively analyzed data from 223 patients treated with definitive concurrent chemoradiotherapy. Treatment-related pneumonitis was graded according to Common Terminology Criteria for Adverse Events version 3.0. Univariate and multivariate analyses were performed to identify predictive factors. Median follow-up was 10.5 months (range, 1.4-58 months). The actuarial incidence of Grade > or =3 pneumonitis was 22% at 6 months and 32% at 1 year. By univariate analyses, lung volume, gross tumor volume, mean lung dose, and relative V5 through V65, in increments of 5 Gy, were all found to be significantly associated with treatment-related pneumonitis. The mean lung dose and rV5-rV65 were highly correlated (p or =3 pneumonitis in the group with V5 42% were 3% and 38%, respectively (p = 0.001). In this study, a number of clinical and dosimetric factors were found to be significantly associated with treatment-related pneumonitis. However, rV5 was the only significant factor associated with this toxicity. Until it is better understood which dose range is most relevant, multiple clinical and dosimetric factors should be considered in treatment planning for non-small-cell lung cancer patients receiving concurrent chemoradiotherapy.
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              Radiation-induced pulmonary toxicity: a dose-volume histogram analysis in 201 patients with lung cancer.

              To relate lung dose-volume histogram-based factors to symptomatic radiation pneumonitis (RP) in patients with lung cancer undergoing 3-dimensional (3D) radiotherapy planning. Between 1991 and 1999, 318 patients with lung cancer received external beam radiotherapy (RT) with 3D planning tools at Duke University Medical Center. One hundred seventeen patients were not evaluated for RP because of or=30 Gy, and normal tissue complication probability derived from the Lyman and Kutcher models) and clinical factors, including tobacco use, age, sex, chemotherapy exposure, tumor site, pre-RT forced expiratory volume in 1 s, weight loss, and performance status. Thirty-nine patients (19%) developed RP. In the univariate analysis, all dosimetric factors (i.e., mean lung dose, volume of lung receiving >or=30 Gy, and normal tissue complication probability) were associated with RP (p range 0.006-0.003). Of the clinical factors, ongoing tobacco use at the time of referral for RT was associated with fewer cases of RP (p = 0.05). These factors were also independently associated with RP according to the multivariate analysis (p = 0.001). Models predictive for RP based on dosimetric factors only, or on a combination with the influence of tobacco use, had a concordance of 64% and 68%, respectively. Dosimetric factors were the best predictors of symptomatic RP after external beam RT for lung cancer. Multivariate models that also include clinical variables were slightly more predictive.

                Author and article information

                Radiat Oncol
                Radiation Oncology (London, England)
                BioMed Central
                21 October 2011
                : 6
                : 140
                [1 ]Radiation Physics Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan Province, PR.China
                [2 ]Department of Thoracic Oncology and Radiation Oncology, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan Province, PR.China
                [3 ]State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan Province, PR.China
                Copyright ©2011 Jiang et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


                Oncology & Radiotherapy
                volumetric modulated arc therapy,lung cancer,target dose distribution,normal tissue toxicity,intensity-modulated radiotherapy


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