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      Dosimetric Comparison between Single and Dual Arc-Volumetric Modulated Arc Radiotherapy and Intensity Modulated Radiotherapy for Nasopharyngeal Carcinoma Using a Simultaneous Integrated Boost Technique

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          Plan quality and performance of dual arc (DA) volumetric modulated arc therapy (VMAT), single arc (SA) VMAT and nine field (9F) intensity modulated radiotherapy were compared using a simultaneous integrated boost (SIB) technique.


          Twelve patients treated in Elekta Synergy Platform (mlci2) by 9F-IMRT were replanned with SA/DA-VMAT using a CMS Monaco Treatment Planning System (TPS) with Monte Carlo simulation. Target delineation was conducted as per Radiation Therapy Oncology Protocols (RTOG0225 and 0615). A 70Gy dose prescribed to PTV70 and 61Gy to PTV61 in 33 fractions was applied for the SIB technique. The conformity index (CI) and homogeneity index (HI) for targets and the mean dose and maximum dose for OAR’s, treatment delivery time (min), monitor units (MUs) per fraction, normal tissue integral dose and patient specific quality assurance were analysed.


          Acceptable target coverage was achieved for PTV70 and PTV61 with all the planning techniques. No significant differences were observed except for D98 (PTV61), CI(PTV70) and HI(PTV61). Maximum dose (Dmax) to the spinal cord was lower in DA-VMAT than 9F-IMRT (p=0.002) and SA-VMAT (p=0.001). D50 (%) of parotid glands was better controlled by 9F-IMRT (p=0.001) and DA-VMAT (p=0.001) than SA-VMAT. A lower mean dose to the larynx was achieved with 9F-IMRT (P=0.001) and DA-VMAT (p=0.001) than with SA-VMAT. DA-VMAT achieved higher CI of PTV70 (P= 0.005) than SA-VMAT. For PTV61, DA-VMAT (P=0.001) and 9F-IMRT (P=0.001) achieved better HI than SA-VMAT. The average treatment delivery times were 7.67mins, 3.35 mins, 4.65 mins for 9F-IMRT, SA-VMAT and DA-VMAT, respectively. No significant difference were observed in MU/fr (p=0.9) and NTID (P=0.90) and the patient quality assurance pass rates were >95% (gamma analysis I3mm, 3%).


          DA-VMAT showed better conformity over target dose and spared the OARs better or equal to IMRT. SA-VMAT could not spare the OARs well. DA-VMAT offered shorter delivery time than IMRT without compromising the plan quality.

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          Most cited references 33

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          Estimates of the worldwide incidence and mortality from 27 cancers in 2008 have been prepared for 182 countries as part of the GLOBOCAN series published by the International Agency for Research on Cancer. In this article, we present the results for 20 world regions, summarizing the global patterns for the eight most common cancers. Overall, an estimated 12.7 million new cancer cases and 7.6 million cancer deaths occur in 2008, with 56% of new cancer cases and 63% of the cancer deaths occurring in the less developed regions of the world. The most commonly diagnosed cancers worldwide are lung (1.61 million, 12.7% of the total), breast (1.38 million, 10.9%) and colorectal cancers (1.23 million, 9.7%). The most common causes of cancer death are lung cancer (1.38 million, 18.2% of the total), stomach cancer (738,000 deaths, 9.7%) and liver cancer (696,000 deaths, 9.2%). Cancer is neither rare anywhere in the world, nor mainly confined to high-resource countries. Striking differences in the patterns of cancer from region to region are observed. Copyright © 2010 UICC.
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            The American Joint Committee on Cancer and the International Union for Cancer Control update the tumor-node-metastasis (TNM) cancer staging system periodically. The most recent revision is the 7th edition, effective for cancers diagnosed on or after January 1, 2010. This editorial summarizes the background of the current revision and outlines the major issues revised. Most notable are the marked increase in the use of international datasets for more highly evidenced-based changes in staging, and the enhanced use of nonanatomic prognostic factors in defining the stage grouping. The future of cancer staging lies in the use of enhanced registry data standards to support personalization of cancer care through cancer outcome prediction models and nomograms.
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              A technique for the quantitative evaluation of dose distributions.

              The commissioning of a three-dimensional treatment planning system requires comparisons of measured and calculated dose distributions. Techniques have been developed to facilitate quantitative comparisons, including superimposed isodoses, dose-difference, and distance-to-agreement (DTA) distributions. The criterion for acceptable calculation performance is generally defined as a tolerance of the dose and DTA in regions of low and high dose gradients, respectively. The dose difference and DTA distributions complement each other in their useful regions. A composite distribution has recently been developed that presents the dose difference in regions that fail both dose-difference and DTA comparison criteria. Although the composite distribution identifies locations where the calculation fails the preselected criteria, no numerical quality measure is provided for display or analysis. A technique is developed to unify dose distribution comparisons using the acceptance criteria. The measure of acceptability is the multidimensional distance between the measurement and calculation points in both the dose and the physical distance, scaled as a fraction of the acceptance criteria. In a space composed of dose and spatial coordinates, the acceptance criteria form an ellipsoid surface, the major axis scales of which are determined by individual acceptance criteria and the center of which is located at the measurement point in question. When the calculated dose distribution surface passes through the ellipsoid, the calculation passes the acceptance test for the measurement point. The minimum radial distance between the measurement point and the calculation points (expressed as a surface in the dose-distance space) is termed the gamma index. Regions where gamma > 1 correspond to locations where the calculation does not meet the acceptance criteria. The determination of gamma throughout the measured dose distribution provides a presentation that quantitatively indicates the calculation accuracy. Examples of a 6 MV beam penumbra are used to illustrate the gamma index.

                Author and article information

                Asian Pac J Cancer Prev
                Asian Pac. J. Cancer Prev
                Asian Pacific Journal of Cancer Prevention : APJCP
                West Asia Organization for Cancer Prevention (Iran )
                : 18
                : 5
                : 1395-1402
                [1 ] Department Of Radiotherapy, Omega Hospitals, Hyderabad
                [2 ] Department Of Physics, VIT University, Vellore, India
                Author notes
                [* ] For Correspondence: siva5434@
                Copyright: © Asian Pacific Journal of Cancer Prevention

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

                Research Article

                sib, imrt, vmat, npc


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