Variations of spatial position and overlap ratio for GTV50 and IGTV of primary thoracic esophageal cancer during radiotherapy:a study based on 4DCT scans
Wang Jinzhi, Li Jianbin, Wang Wei, Zhang Yingjie, Ding Yun, Liu Tonghai, Shang Dongping.
Department of Radiation Oncology, Shandong Cancer Hospital;Medicine and Life Sciences College of Shandong Academy of Medical Sciences, Ji′nan University, Ji′nan 250117, China
Abstract：Objective To investigate the variations of the spatial position and overlap ratio for gross tumor volume (respiratory phase 50%)(GTV50) and internal gross tumor volume (IGTV) of primary thoracic esophageal cancer during conventional fractionated radiotherapy based on repeated four-dimensional computed tomography (4DCT) scans. Methds Thirty-three patients with thoracic esophageal cancer underwent contrast-enhanced 4DCT scans before radiotherapy and at the 10th and 20th fractions of radiotherapy. Scans were registered to the baseline 4DCT scan using bony landmarks. The GTV50 was delineated by the same radiotherapist on each 4DCT imaging data set, and the IGTV was constructed accordingly. The target volume, degree of inclusion (DI), and matching index (MI) were compared in different phases. Results The volumes of GTV50 and IGTV decreased along with treatment course. No significant changes in the centroid position were observed for the GTV50 and IGTV. The median DIs of the target volumes at the 10th and 20th fractions in the original target volume were 0.75 and 0.63(P=0.000) for GTV50 and were 0.79 and 0.66(P=0.000) for IGTV, while the median MIs were 0.61 and 0.56(P=0.002) for GTV50 and were 0.68 and 0.58(P=0.005) for IGTV. A positive correlation between the variation of volume ratio and the variation of DI was found for GTV50 and IGTV (r=0.632, r=0.783), and the variation of volume ratio was also positively correlated with the variation of MI (r=0.387, r=0.483);the 3D vector was negatively correlated with the MI (r=－0.455, r=－0.438). Conclusions During conventional fractionated radiotherapy, the variation of spatial position is less than 0.8 cm for GTV50 and IGTV of primary thoracic esophageal cancer, and the decline of the target leads to varying degrees of decreases in DI and the MI.
Wang Jinzhi,Li Jianbin,Wang Wei et al. Variations of spatial position and overlap ratio for GTV50 and IGTV of primary thoracic esophageal cancer during radiotherapy:a study based on 4DCT scans[J]. Chinese Journal of Radiation Oncology, 2014, 23(6): 491-494.
[1] Wang W, Li J, Zhang Y, et al. Comparison of patient-specific internal gross tumor volume for radiation treatment of primary esophageal cancer based separately on three-dimensional and four-dimensional computed tomography images[J]. Dis Esophagus,2014,In press. [2] Zhao KL, Liao Z, Bucci MK, et al. Evaluation of respiratory induced target motion for esophageal tumors at the gastroesophageal junction[J]. Radiother Oncol,2007,84:283-289. [3] 李奉祥,李建彬,张英杰,等.四维影像在肿瘤放射治疗中的应用[J].中华肿瘤杂志,2011,33:721-725. [4] Hof H, Rhein B, Haering P, et al. 4D-CT-based target volume definition in stereotactic radiotherapy of lung tumors:comparison with a conventional technique using individual margins[J]. Radiother Oncol,2009,93:419-423. [5] Ezhil M, Vedam S, Balter P, et al. Determination of patient-specific internal gross tumor volumes for lung cancer using four-dimensional computed tomography[J].Radiat Oncol,2009,4:l-14. [6] Harris EJ, Donovan EM, Yarnold JR, et al.Characterization of target volume changes during breast radiotherapy using implanted fiducial markers and portal imaging[J].Int J Radiat Oncol Biol Phys,2009,73:958-966. [7] Britton KR, Starkschall G, Tucker SL, et al. Assessment of gross tumor volume regression and motion changes during radiotherapy for non-small cell lung cancer as measured by four-dimensional computed tomography[J]. Int J Radiat Oncol Biol Phys,2007,68:1036-1046. [8] Matusgi K, Narita Y, Sawada A, et al. Measurement of interfraction variations in position and size of target volumes in stereotactic body radiotherapy for lung cancer[J]. Int J Radiat Oncol Biol Phys,2009,75:543-548. [9] Sonke JJ, Lebesque J, van Herk M, et al. Variability of four-dimensional computed tomography patient models[J]. Int J Radiat Oncol Biol Phys,2008,70:590-598. [10] Michalski D, Sontag M, Li F, et al. Four-dimensional computed tomography-based interfractional reproducibility study of lung tumor intrafractional motion[J]. Int J Radiat Oncol Biol Phys,2008,71:714-724. [11] Chang J, Mageras GS, Yorke E, et al. Observation of interfractional variations in lung tumor position using respiratory gated and ungated megavoltage cone-beam computed tomography[J]. Int J Radiat Oncol Biol Phys,2007,67:1548-1558. [12] Wang J, Lin SH, Dong L, et al. Quantifying the interfractional displacement of the gastroesophageal junction during radiation therapy for esophageal cancer[J]. Int J Radiat Oncol Biol Phys,2012,83:273-280. [13] 王金之,李建彬,王玮,等.基于放疗疗程中重复4D-CT扫描胸段食管癌原发肿瘤靶区体积变化的研究[J].中华放射医学与防护杂志,2013,33:403-404. [14] 王奇峰,章文成,陈辛元,等.食管癌简化调强放疗中靶体积变化及对初始计划剂量学影响[J].中华放射肿瘤学杂志,2010,19:512-516. [15] 宋斌斌,陆雪官,钱建军,等.食管癌分次放疗期间靶区不确定性研究[J].中华放射肿瘤学杂志,2009,18:188-190. [16] Underberg RW, Lagerwaard FJ, van Tinteren H, et al. Time trends in target volumes for stage Ⅰ non-small cell lung cancer after stereotactic radiotherapy[J]. Int J Radiat Oncol Biol Phys,2006,64:1221-1228.
2014, Vol. 23 
