AbstractObjective To use helical tomotherapy (HT) for determining the difference between actual doses and planning doses to the target volume and organs at risk (OARs) in patients with nasopharyngeal carcinoma receiving radiotherapy, and to provide guidance for the clinical treatment. Methods Localization and delineation of the target volume and OARs were performed by computed tomography (CT) in 21 patients with nasopharyngeal carcinoma receiving radical radiotherapy using HT. All patients underwent megavoltage CT (MVCT) scan prior to treatment. The obtained MVCT images were used for dose reconstruction in the adaptive module of HT, in which the actual dose was obtained and the non-image-guided dose was simulated. Each single dose distribution and the corresponding CT image were sent to software MIM6.0 for superimposition, and the overall dose was obtained. The initial plan, image-guided plan, and non-image-guided plan were named Plan-1, 2, and 3, respectively. The dose distribution in thetarget volume and OARs was compared between the three plans with t-test or wilcoxon test. Results Compared with those in Plan-1, the D98 values for the planning gross tumor volume (PGTV) and planning target volume (PTV) in Plan-2 were significantly reduced by 1.16% and 2.3%, respectively (P=0.025;P=0.043);the volumes of the left and right parotids in Plan-2 were significantly reduced by 46.0% and 46.5% on average, respectively (P=0.000);the distances between the midline and the center-of-mass for left and right parotids were significantly reduced by 6.9% and 6.5%, respectively (P=0.000);the V26 and Dmean for both parotid glands were significantly elevated by 32.8% and 25.2%, respectively (P=0.000). Compared with those in Plan-1, the D98 values for PGTV, PTV-1, and PTV-2 in Plan-3 were significantly reduced by 2.0%, 1.9%, and 2.4%, respectively (P=0.001;P=0.007;P=0.036);the V26 and Dmean for both parotid glands in Plan-3 were significantly elevated by 33.6% and 25.3%, respectively (P=0.000);Dmax to the spinal cord was significantly increased by 6.9%(P=0.005). There was no significant difference in D2 to the spinal cord between Plan-2 and Plan-1(P=0.392). Conclusions The doses to both parotid glands increase during HT for nasopharyngeal carcinoma, which is closely associated with the shift of the parotid glands toward the midline. Image-guided radiotherapy does not enhance the dose to the target volume, but reduces the dose to the spinal cord.
Fund:Capital Health Research and Development Special Fund (2011502105)
Corresponding Authors:
Wang Yadi,Email:wangyadi@hotmail.com
E-mail: wangyadi@hotmail.com
Cite this article:
Cao Xinge,Wang Yadi,Zhang Yongqian et al. A dosimetric study of helical tomotherapy for nasopharyngeal carcinoma[J]. Chinese Journal of Radiation Oncology, 2016, 25(8): 802-806.
Cao Xinge,Wang Yadi,Zhang Yongqian et al. A dosimetric study of helical tomotherapy for nasopharyngeal carcinoma[J]. Chinese Journal of Radiation Oncology, 2016, 25(8): 802-806.
[1] Lu T,Luo W,Zhao C,et al. Retrospective analysis of 934 primary nasopharyngeal carcinoma (NPC) patients treated with conventional external beam radiotherapy alone[J].Int J Radiat Oncol Biol Phys,2004,60(1 Suppl):S508-S509.DOI:10.1016/j.ijrobp.2004.07.451 [2] 赵充,肖巍魏,韩非,等.419例鼻咽癌患者IMRT疗效和影响[J].中华放射肿瘤学杂志,2010,19(3):191-196.DOI:10.3760/cma.j.issn.1004-4221.2010.03.005 Zhao C,Xiao WW,Han F,et al. Long-term outcome and prognostic factors of patients with nasopharyngeal carcinoma treated with intensity-modulated radiation therapy[J].Chin J Radiat Oncol,2010,19(3):191-196.DOI:10.3760/cma.j.issn.1004-4221.2010.03.005 [3] 冯梅,范子煊,黎杰,等.582例鼻咽癌IMRT5年远期疗效及预后分析[J].中华放射肿瘤学杂志,2011,20(5):369-373.DOI:10.3760/cma.j.issn.1004-4221.2011.05.003 Feng M,Fan ZX,Li J,et al. Long-term results and prognostic factors in 582 nasopharyngeal carcinoma treated by intensitymodulated radiotherapy[J].Chin J Radiat Oncol,2011,20(5):369-373.DOI:10.3760/cma.j.issn.1004-4221.2011.05.003 [4] Welsh JS,Lock M,Harari PM,et al. Clinical implementation of adaptive helical tomotherapy:a unique approach to image-guided intensity modulated radiotherapy[J].Technol Cancer Res Treat,2006,5(5):465-479.DOI:10.1177/153303460600500503 [5] Shah AP,Langen KM,Ruchala KJ,et al. Patient dose from megavoltage computed tomography imaging[J].Int J Radiat Oncol Biol Phys,2008,70(5):1579-1587.DOI:10.1016/j.ijrobp.2007.11.048 [6] Pukala J,Meeks SL,Bova FJ,et al. The effect of temporal HU variations on the uncertainty of dose recalculations performed on MVCT images[J].Phys Med Biol,2011,56(24):7829-7841.DOI:10.1088/0031-9155/56/24/010 [7] Guckenberger M,Richter A,Wilbert J,et al. Adaptive radiotherapy for locally advanced non-small-cell lung cancer does not underdose the microscopic disease and has the potential to increase tumor control[J].Int J Radiat Oncol Biol Phys,2011,81(4):e275-e282.DOI:10.1016/j.ijrobp.2011.01.067 [8] 张勇乾,张富利,王雅棣,等.头颈部肿瘤HT剂量学研究[J].中华放射肿瘤学杂志,2014,23(6):519-522.DOI:10.3760/cma.j.issn.1004-4221.2014.06.016 Zhang YQ,Zhang FL,Wang YD,et al. Dosimetric evaluation for head and neck cancer patients treated with helical TomoTherapy[J].Chin J Radiat Oncol,2014,23(6):519-522.DOI:10.3760/cma.j.issn.1004-4221.2014.06.016 [9] Lu J,Ma YD,Chen JH,et al. Assessment of anatomical and dosimetric changes by a deformable registration method during the course of intensity-modulated radiotherapy for nasopharyngeal carcinoma[J].J Radiat Res,2014,55(1):97-104.DOI:10.1093/jrr/rrt076 [10] Duma MN,Kampfer S,Schuster T,et al. Do we need daily image-guided radiotherapy by megavoltage computed tomography in head and neck helical tomotherapy? The actual delivered dose to the spinal cord[J].Int J Radiat Oncol Biol Phys,2012,84(1):283-288.DOI:10.1016/j.ijrobp.2011.10.073 [11] Han CH,Chen YJ,Liu A,et al. Actual dose variation of parotid glands and spinal cord for nasopharyngeal cancer patients during radiotherapy[J].Int J Radiat Oncol Biol Phys,2008,70(4):1256-1262.DOI:10.1016/j.ijrobp.2007.10.067 [12] Voordeckers M,Farrag A,Everaert H,et al. Parotid gland sparing with helical tomotherapy in head-and-neck cancer[J].Int J Radiat Oncol Biol Phys,2012,84(2):443-448.DOI:10.1016/j.ijrobp.2011.11.070 [13] Tham IWK,Hee SW,Yeo RMC,et al. Treatment of nasopharyngeal carcinoma using intensity-modulated radiotherapy-the national cancer center Singapore experience[J].Int Radiat Oncol Biol Phys,2009,75(5):1481-1486.DOI:10.1016/j.ijrobp.2009.01.018 [14] Elstrm UV,Wysocka BA,Muren LP,et al. Daily kV cone-beam CT and deformable image registration as a method for studying dosimetric consequences of anatomic changes in adaptive IMRT of head and neck cancer[J].Acta Oncol,2010,49(7):1101-1108.DOI:10.3109/0284186X.2010.500304 [15] 曹建忠,罗京伟,徐国镇,等.鼻咽癌IMRT中靶区和正常器官变化规律及临床意义探讨[J].中华放射肿瘤学杂志,2007,16(2):81-85.DOI:10.3760/j.issn:1004-4221.2007.02.001 Cao JZ,Luo JW,Xu GZ,et al. Probe into the clinical significance of target volume and change of the normal organs in image-guided radiotherapy for nasopharyngeal carcinoma[J].Chin J Radiat Oncol,2007,16(2):81-85.DOI:10.3760/j.issn:1004-4221.2007.02.001 [16] Duma MN,Kampfer S,Wilkens JJ,et al. Comparative analysis of an image-guided versus a non-image-guided setup approach in terms of delivered dose to the parotid glands in head-and-neck cancer IMRT[J].Int J Radiat Oncol Biol Phys,2010,77(4):1266-1273.DOI:10.1016/j.ijrobp.2009.09.047 [17] Lee C,Langen KM,Lu WG,et al. Assessment of parotid gland dose changes during head and neck cancer radiotherapy using daily megavoltage computed tomography and deformable image registration[J].Int J Radiat Oncol Biol Phys,2008,71(5):1563-1571.DOI:10.1016/j.ijrobp.2008.04.013
2016, Vol. 25 
