Comparison of intensity modulated radiation therapy (IMRT) treatment techniques for nasopharyngeal carcinoma
Comparison of intensity modulated radiation therapy (IMRT) treatment techniques for nasopharyngeal carcinoma
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DOI：
10.1002/ijc.1004
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发表时间：
2001-04-20
影响因子：
6.4
通讯作者：
Low, D
中科院分区：
文献类型：
--
作者：
Cheng, JCH;Chao, KSC;Low, D
研究鼻咽癌连续适形调强放射治疗(IMRT)和固定野调强放射治疗(IMRT)的靶区覆盖和正常组织保留情况，并与常规放射治疗方法进行比较。Mallinckrodt放射研究所的12例鼻咽癌患者(T2-4N1-3M0)接受了计算机断层扫描模拟。然后将图像传输到虚拟仿真工作站计算机进行目标轮廓绘制。靶区肿瘤体积(GTV)为鼻咽部原发肿瘤(GTV(NP))，剂量为70Gy；颈部肿大结节(GTV，LN)，剂量为70Gy.关键器官，包括腮腺、脊髓、脑干、下颌骨和脑下垂体也被勾画出来。常规射束装置的设计遵循组间(SWOG，RTOG，ECOG)NPC研究0099指南，其中剂量规定到中心轴，靶区体积以获得规定剂量+/-10%为目标。采用类似的剂量学标准评估调强放疗的靶区复盖能力。序列放射治疗计划使用0.86厘米宽的多叶片准直器，而具有五个等间距固定门架角度的动态多叶准直器系统被指定用于固定光束调强放疗。在三维或调强放射治疗计划计算机系统中，从每个器官的剂量-体积直方图中获得接受特定预定阈值剂量的每个关键器官的分数体积。统计分析(配对t检验)用于检验统计学意义。我们发现，连续放射治疗达到了与传统技术相似的目标体积覆盖率(97.8+/-2.3%vs.98.9+/-1.3%)。静电场调强放射治疗技术(5个等间隔野)较差，92.1+/-8.6%的部分GTV(NP)接受70Gym 10%剂量(P<；0.05)。然而，放射治疗、固定野调强放疗和常规治疗的GTV覆盖率分别为96.1 3.2%、87.7+/-10.6%和42.2+/-21%(P<0.05)。采用调强放射治疗后，60GyCTV覆盖率也有明显提高。放射治疗组、固定野调强放疗组和常规治疗组分别有66.6+/-15%、48.3+/-4%和93+/-10%的腮腺体积接受了>30Gy的放射治疗(Pc0.05)。固定野调强放射治疗的腮腺保留效果最好，但靶区复盖率较低。两种调强放射治疗技术都能更好地保护脑下垂体、下颌骨、脊髓和脑干。这些令人鼓舞的剂量学结果证实了逆计划调强放射治疗在鼻咽癌治疗中的理论优势。我们发现，与传统的射束安排相比，原发灶的靶区覆盖率得到了维持，而结节覆盖率得到了改善。调强放疗节省腮腺的能力是令人兴奋的，我们机构目前正在进行一项前瞻性的临床研究，以解决预防鼻咽癌患者口干症和改善生活质量所需的最佳腮腺剂量-体积，(C)2001 Wiley-Liss，Inc.。
We studied target volume coverage and normal tissue sparing of serial tomotherapy intensity modulated radiation therapy (IMRT) and fixed-field IMRT for nasopharyngeal carcinoma (NPC), as compared with those of conventional beam arrangements. Twelve patients with NPC (T2-4N1-3M0) at Mallinckrodt Institute of Radiology underwent computed tomography simulation. Images were then transferred to a virtual simulation workstation computer for target contouring. Target gross tumor volumes (GTV) were primary nasopharyngeal tumor (GTV(NP)) with a prescription of 70 Gy, grossly enlarged cervical nodes (GTV(LN)) with a prescription of 70 Gy, and the uninvolved cervical lymphatics [designated as the clinical tumor volume (CTV)] with a prescription of 60 Gy. Critical organs, including the parotid gland, spinal cord, brain stem, mandible, and pituitary gland, were also delineated. Conventional beam arrangements were designed following the guidelines of Intergroup (SWOG, RTOG, ECOG) NPC Study 0099 in which the dose was prescribed to the central axis and the target volumes were aimed to receive the prescribed dose +/- 10%. Similar dosimetric criteria were used to assess the target volume coverage capability of IMRT. Serial tomotherapy IMRT was planned using a 0.86-cm wide multivane collimator, while a dynamic multileaf collimator system with five equally spaced fixed gantry angles was designated for fixed-beam IMRT. The fractional volume of each critical organ that received a certain predefined threshold dose was obtained from dose-volume histograms of each organ in either the three-dimensional or IMRT treatment planning computer systems. Statistical analysis (paired t-test) was used to examine statistical significance. We found that serial tomotherapy achieved similar target volume coverage as conventional techniques (97.8 +/- 2.3% vs. 98.9 +/- 1.3%). The static-field IMRT technique (five equally spaced fields) was inferior, with 92.1 +/- 8.6% fractional GTV(NP) receiving 70 Gy m 10% dose (P < 0.05). However, GTV,, coverage of 70 Gy was significantly better with both IMRT techniques (96.1 3.2%, 87.7 +/- 10.6%, and 42.2 +/- 21% for tomotherapy, fixed-field IMRT, and conventional therapy, respectively). CTV coverage of 60 Gy was also significantly better with the IMRT techniques. Parotid gland sparing was quantified by evaluating the fractional volume of parotid gland receiving more than 30 Gy; 66.6 +/- 15%, 48.3 +/- 4%, and 93 +/- 10% of the parotid volume received more than 30 Gy using tomotherapy, fixed-field IMRT, and conventional therapy, respectively (P c 0.05). Fixed-field IMRT technique had the best parotid-sparing effect despite less desirable target coverage. The pituitary gland, mandible, spinal cord, and brain stem were also better spared by both IMRT techniques. These encouraging dosimetric results substantiate the theoretical advantage of inverse-planning IMRT in the management of NPC. We showed that target coverage of the primary tumor was maintained and nodal coverage was improved, as compared with conventional beam arrangements. The ability of IMRT to spare the parotid glands is exciting, and a prospective clinical study is currently underway at our institution to address the optimal parotid dose-volume needs to be spared to prevent xerostomia and to improve the quality of life in patients with NPC, (C) 2001 Wiley-Liss, Inc.