RapidArc® vs intensity-modulated radiation therapy for hepatocellular carcinoma: A comparative planning study

Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Republic of Korea.
The British journal of radiology (Impact Factor: 2.03). 07/2012; 85(1015):e323-9. DOI: 10.1259/bjr/19088580
Source: PubMed


The purpose of this study is to compare the dose-volumetric results of RapidArc (RA Varian Medical Systems, Palo Alto, CA) with those of intensity-modulated radiation therapy (IMRT) for hepatocellular carcinoma.
20 patients previously treated for hepatocellular carcinoma were the subjects of this planning study. 10 patients were treated for portal vein tumour thrombosis (Group A), and 10 patients for primary liver tumour (Group B). Prescription dose to the planning target volume was 54 Gy in 30 fractions, and the planning goal was to deliver more than 95% of prescribed dose to at least 95% of planning target volume.
In Group A, mean doses to liver were increased with RA vs IMRT (22.9 Gy vs 22.2 Gy, p=0.0275). However, V(30 Gy) of liver was lower in RA vs IMRT (31.1% vs 32.1%, p=0.0283). In Group B, in contrast, neither mean doses nor V(30 Gy) of liver significantly differed between the two plans. V(35 Gy) of duodenum and V(20 Gy) of kidney were decreased with RA in Groups A and B, respectively (p=0.0058 and 0.0124, respectively). Both maximal doses to spinal cord and monitor unit were significantly lower in the RA plan, regardless of the group.
The dose-volumetric results of RA vs IMRT were different according to the different target location within the liver. In general, RA tended to be more effective in the sparing of non-liver organs at risk such as duodenum, kidney, and/or spinal cord. Moreover, RA was more efficient in the treatment delivery than IMRT in terms of total monitor unit used.

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Available from: Jong Min Park, Jan 28, 2015
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    • "Volumetric modulated arc therapy (VMAT) delivers prescription doses to target volumes while minimizing the dose to normal tissue by modulating photon beams through modulations of multi-leaf collimator (MLC) positions, gantry rotation speed and dose-rate simultaneously (Brahme 1988, Otto 2008). Recently, VMAT has been widely adopted in the clinic due to its ability to rapidly deliver dose distributions which are equal to or better than those of intensity modulated radiation therapy (IMRT) (Park et al 2012, 2014a, 2014c, Kim et al 2014, Mattes et al 2014, Heo et al 2015). For VMAT, the mechanical uncertainty of MLC movements, gantry rotations and beam control systems as well as inaccurate dose calculations of small or irregular fields result in discrepancies between planned dose distributions as intended to be delivered to the patient, and the actual delivery to the patient (Ezzell et al 2003, Fredh et al 2013, Heilemann et al 2013, Kim et al 2014, Heo et al 2015, Park et al 2015a). "
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    ABSTRACT: The aim of this study is to present a modulation index considering both mechanical and dose calculation uncertainties for volumetric modulated arc therapy (VMAT). As a modulation index considering only mechanical uncertainty of VMAT, MIt has been previously suggested. In this study, we developed a weighting factor which represents dose calculation uncertainty based on the aperture shapes of fluence maps at every control point of VMAT plans. In order to calculate the weighting factor, the thinning algorithm of image processing techniques was applied to measure field aperture irregularity. By combining this weighting factor with the previously suggested modulation index, MIt, comprehensive modulation index (MIc) was designed. To evaluate the performance of MIc, gamma passing rates, differences in mechanical parameters between plans and log files and differences in dose-volume parameters between plans and the plans reconstructed from log files were acquired with a total of 52 VMAT plans. Spearman's correlation coefficients (rs) between the values of MIc and measures of VMAT delivery accuracy were calculated. The rs values of MIc (f = 0.5) to global gamma passing rates with 2%/2 mm, 1%/2 mm and 2%/1 mm were -0.728,-0.847 and -0.617, respectively (p < 0.001). Those to local gamma passing rates were -0.765,-0.767 and -0.748, respectively (p < 0.001). The rs values of MIc (f = 0.5) to multi-leaf collimator and gantry angle errors were 0.800 and -0.712, respectively (p < 0.001). The MIc (f = 0.5) showed a total of 20 rs values (p < 0.05) to the differences in dose-volumetric parameters from a total of 35 tested cases. The MIc (f = 0.5) demonstrated considerable power to predict VMAT delivery accuracy showing strong correlations to various measures of VMAT delivery accuracy.
    Full-text · Article · Sep 2015 · Physics in Medicine and Biology
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    • "Volumetric modulated arc therapy (VMAT) as well as intensity modulated radiation therapy (IMRT) modulate photon beam intensities to acquire optimal dose distributions for treatment. By modulating photon beam intensity, a sufficient prescription dose to control tumor cells can be delivered while reducing unnecessary irradiation of normal tissue to prevent complications [1] [2] [3] [4] [5] [6] [7]. "
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    ABSTRACT: Purpose: Textural features calculated from various segmental fluences of volumetric modulated arc therapy (VMAT) plans were optimized to enhance its performance to predict plan delivery accuracy. Methods: Twenty prostate and twenty head and neck VMAT plans were selected retrospectively. Fluences were generated for each VMAT plan by summations of segments at sequential groups of control points. The numbers of summed segments were 5, 10, 20, 45, 90, 178 and 356. For each fluence, we investigated 6 textural features: angular second moment, inverse difference moment, contrast, variance, correlation and entropy (particular displacement distances, d = 1, 5 and 10). Spearman's rank correlation coefficients (rs ) were calculated between each textural feature and several different measures of VMAT delivery accuracy. Results: The values of rs of contrast (d = 10) with 10 segments to both global and local gamma passing rates with 2%/2 mm were 0.666 (p <. 0.001) and 0.573 (p <. 0.001), respectively. It showed rs values of -0.895 (p <. 0.001) and 0.727 (p <. 0.001) to multi-leaf collimator positional errors and gantry angle errors during delivery, respectively. The number of statistically significant rs values (p <. 0.05) to the changes in dose-volumetric parameters during delivery was 14 among a total of 35 tested parameters. Conclusions: Contrast (d = 10) with 10 segments showed higher correlations to the VMAT delivery accuracy than did the conventional modulation indices.
    Full-text · Article · Sep 2015 · Physica Medica
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    • "and the median survival period ranged from 6.7–10.7 months [14–20]. In addition, intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT), and tomotherapy were also employed for treating PVTT [21, 22]. However, to the best of our knowledge, dose-escalation studies using VMAT for PVTT have not been reported. "
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    ABSTRACT: We created volumetric-modulated arc therapy (VMAT) plans for portal vein tumor thrombus (PVTT) in hepatocellular carcinoma, and compared the results with those from three-dimensional conformal radiotherapy (3D-CRT) and rotational conformal radiotherapy (R-CRT) plans. CT scan data from 10 consecutive patients with PVTT treated with 3D-CRT between January 2008 and January 2010 were utilized in the analysis. We analyzed the dosimetric properties of the plans for the 10 patients using the three different techniques with three different isocenter doses of 50, 56 and 60 Gy in 2-Gy fractions. The D95, Dmean, homogeneity index and conformity index were compared for the planning target volume (PTV). The Dmean, V20 and V30 were also compared for normal livers. The monitor units (MUs) and the treatment time were also evaluated. The normal liver V30 for VMAT was significantly less than that for 3D-CRT for the prescribed doses of 56 and 60 Gy (P < 0.05). It was also found that the normal liver V30 resulting from 3D-CRT was prohibitively increased when the prescribed dose was increased in two steps. For PTV D95, we found no significant differences between the three techniques for the 50- and 56-Gy prescriptions, or between VMAT and the other techniques for the 60-Gy prescription. The differences in the MUs and treatment times were not statistically significant between VMAT and 3D-CRT. We have demonstrated that VMAT may be a more advantageous technique for dose escalation reaching 60 Gy in the treatment of PVTT due to the reduced normal liver V30.
    Full-text · Article · Feb 2013 · Journal of Radiation Research
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