Comparison of inverse-planned three-dimensional conformal radiotherapy and intensity-modulated radiotherapy for non-small-cell lung cancer

PURPOSE: Lungs are the major dose-limiting organ during radiotherapy (RT) for non-small-cell lung cancer owing to the development of pneumonitis. This study compared intensity-modulated RT (IMRT) with three-dimensional conformal RT (3D-CRT) in reducing the dose to the lungs. METHODS: Ten patients with localized non-small-cell lung cancer underwent computed tomography (CT). The planning target volume (PTV) was defined and the organs at risk were outlined. An inverse-planning program, AutoPlan, was used to design the beam angle-optimized six-field noncoplanar 3D-CRT plans. Each 3D-CRT plan was compared with a series of five IMRT plans per patient. The IMRT plans were created using a commercial algorithm and consisted of a series of three, five, seven, and nine equidistant coplanar field arrangements and one six-field noncoplanar plan. The planning objectives were to minimize the lung dose while maintaining the dose to the PTV. The percentage of lung volume receiving >20 Gy (V20) and the percentage of the PTV covered by the 90% isodose (PTV90) were the primary endpoints. The PTV90/V20 ratio was used as the parameter accounting for both the reduction in lung volume treated and the PTV coverage. RESULTS: All IMRT plans, except for the three-field coplanar plans, improved the PTV90/V20 ratio significantly compared with the optimized 3D-CRT plan. Nine coplanar IMRT beams were significantly better than five or seven coplanar IMRT beams, with an improved PTV90/V20 ratio. CONCLUSION: The results of our study have shown that IMRT can reduce the dose to the lungs compared with 3D-CRT by improving the conformity of the plan.     

胃癌术后放疗方式对肾脏剂量学影响的比较研究

目的:比较胃癌术后三维适形放疗(3D-CRT)与调强适形放疗(IMRT)对肾脏剂量学的分布影响.方法:选择9例根治术后的进展期胃癌患者,应用Pinnacal三维计划系统(TPS)分别为每例患者设计4野3D-CRT和5、7野IMRT,所有计划给予处方剂量95％的计划靶体积(PTV)＞45 Gy; IMRT同时要求99％的PTV体积＞42.75 Gy.应用等剂量曲线及剂量体积直方图(DVH)比较各个计划之间靶区剂量的分布和肾脏的剂量受量差异.结果:4野3D-CRT和5、7野IMRT的靶区V45分别为0.96±0.03、0.95±0.02和0.95±0.02.所有计划靶区均满足处方剂量,与4野3D-CRT相比,IMRT明显提高靶区的剂量的均匀性(HI)和适形度(CI),并且降低双侧肾脏18 Gy的剂量体积百分比(V18),但在低剂量(10 Gy)体积百分比(V10)3种放射方式之间差异无统计学意义,P＞0.05.5和7野IMRT之间不论在靶区剂量分布还是危及器官的剂量受量上均差异无统计学意义,P＞0.05.结论:与3D-CRT比较,IMRT明显提高靶区均匀性,降低肾脏剂量受量和剂量体积百分比,但在V10上3种计划间差异无统计学意义.     

Is intensity-modulated radiotherapy better than conventional radiation treatment and three-dimensional conformal radiotherapy for mediastinal masses in patients with Hodgkin’s disease,and is there a role for beam orientation optimization and dose constraints assigned to virtual volumes?

PURPOSE: To evaluate the role of beam orientation optimization and the role of virtual volumes (VVs) aimed at protecting adjacent organs at risk (OARs), and to compare various intensity-modulated radiotherapy (IMRT) setups with conventional treatment with anterior and posterior fields and three-dimensional conformal radiotherapy (3D-CRT). METHODS AND MATERIALS: Patients with mediastinal masses in Hodgkin's disease were treated with combined modality therapy (three to six cycles of adriamycin, bleomycin, vinblastine, and dacarbazine [ABVD] before radiation treatment). Contouring and treatment planning were performed with Somavision and CadPlan Helios (Varian Systems, Palo Alto, CA). The gross tumor volume was determined according to the prechemotherapy length and the postchemotherapy width of the mediastinal tumor mass. A 10-mm isotropic margin was added for the planning target volume (PTV). Because dose constraints assigned to OARs led to unsatisfactory PTV coverage, VVs were designed for each patient to protect adjacent OARs. The prescribed dose was 40 Gy to the PTV, delivered according to guidelines from International Commission on Radiation Units and Measurements Report No. 50. Five different IMRT treatment plans were compared with conventional treatment and 3D-CRT. RESULTS: Beam orientation was important with respect to the amount of irradiated normal tissues. The best compromise in terms of PTV coverage and protection of normal tissues was obtained with five equally spaced beams (5FEQ IMRT plan) using dose constraints assigned to VVs. When IMRT treatment plans were compared with conventional treatment and 3D-CRT, dose conformation with IMRT was significantly better, with greater protection of the heart, coronary arteries, esophagus, and spinal cord. The lungs and breasts in women received a slightly higher radiation dose with IMRT compared with conventional treatments. The greater volume of normal tissue receiving low radiation doses could be a cause for concern. CONCLUSIONS: The 5FEQ IMRT plan with dose constraints assigned to the PTV and VV allows better dose conformation than conventional treatment and 3D-CRT, notably with better protection of the heart and coronary arteries. Of concern is the "spreading out" of low doses to the rest of the patient's body.     

直肠癌术前三维适形放疗和五野调强放疗的剂量学比较研究

目的:探讨直肠癌术前三维适形放疗(3D-CRT)和五野调强放射治疗(5F-IMRT)计划的剂量学特点,及其术前放疗较佳的放疗技术.方法:对27例拟行术前放疗的直肠癌患者进行3D-CRT和IMRT 2套治疗计划设计,比较2种放疗计划的靶区剂量学特点以及小肠、膀胱和双侧股骨头等正常组织的受照射剂量及体积.结果:5F-IMRT计划中适形指数(CI)为(0.805±0.050),大于3D-CRT(0.698±0.060),P＜0.001;2种计划的GTV均匀指数(HI)值均非常接近1,差异无统计学意义;5F-IMRT计划中HICTV和HIPTV值均分别小于3D-CRT计划,P＜0.05.5F-IMRT计划中小肠D5、Dmin和Dmax与3D-CRT相应参数差异无统计学意义,但Dmean低于3D-CRT,P＜0.05;5F-IMRT计划中小肠V30高于3D-CRT,而V50则前者低于后者,差距也有统计学意义,P=0.041.类似的结果也见于膀胱.5F-IMRT计划中左、右股骨头Dmin和Dmax均低于3D-CRT,V40也明显小于3D-CRT,P＜0.05.结论:直肠癌术前放疗5F-IMRT计划剂量分布适形性及均匀性明显优于3D-CRT,且能更好地保护直肠周边邻近的正常组织器官.     

Accelerated partial-breast intensity-modulated radiotherapy results in improved dose distribution when compared with three-dimensional treatment-planning techniques

PURPOSE: To compare dose distribution and normal tissue sparing in partial-breast treatment using three-dimensional conformal radiotherapy (3D-CRT) vs. intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS: Sixty-three patients with Tis-1N0M0 breast cancer were treated on a Phase II prospective accelerated partial-breast IMRT protocol at two facilities between April 2004 and January 2006. Fifty-six patients had data sets sufficient to adequately contour all structures. These cases were subsequently replanned with 3D-CRT techniques using the same contours, to compare the dose distribution patterns of 3D-CRT vs. IMRT. RESULTS: The average planning target volume (PTV) to ipsilateral breast (IB) ratio was 24% (range, 7-58%). The average volume of IB receiving 25%, 50%, 75%, and 100% of the prescribed dose was 4.0%, 5.0%, 5.5%, and 10.5% less with IMRT than with 3D (p < 0.01). The dose reduction to normal breast was further improved in the subset of patients whose PTV to IB ratio was >25%, and in patients with contoured breast volume <750 cm(3). No difference was detected in delivery to the lumpectomy cavity or clinical target volume. The PTV volume receiving 95% of the dose was higher in the 3D conformal plans (p < 0.01), but no significant difference was observed in the PTV volume receiving 90% (p = 0.17). The irradiated heart and lung volumes were small with both techniques but also favored IMRT. CONCLUSIONS: In T1N0 patients treated with external beam partial-breast radiotherapy, IMRT improves normal tissue sparing in the ipsilateral breast compared with 3DRT, without compromising dose delivery to the lumpectomy cavity and clinical target volume.     

Intensity-modulated radiotherapy in nasopharyngeal carcinoma: dosimetric advantage over conventional plans and feasibility of dose escalation

PURPOSE: To compare intensity-modulated radiotherapy (IMRT) with two-dimensional RT (2D-RT) and three-dimensional conformal radiotherapy (3D-CRT) treatment plans in different stages of nasopharyngeal carcinoma and to explore the feasibility of dose escalation in locally advanced disease. MATERIALS AND METHODS: Three patients with different stages (T1N0M0, T2bN2M0 with retrostyloid extension, and T4N2M0) were selected, and 2D-RT, 3D-CRT, and IMRT treatment plans (66 Gy) were made for each of them and compared with respect to target coverage, normal tissue sparing, and tumor control probability/normal tissue complication probability values. In the Stage T2b and T4 patients, the IMRT 66-Gy plan was combined with a 3D-CRT 14-Gy boost plan using a 3-mm micromultileaf collimator, and the dose-volume histograms of the summed plans were compared with their corresponding 66-Gy 2D-RT plans. RESULTS: In the dosimetric comparison of 2D-RT, 3D-CRT, and IMRT treatment plans, the T1N0M0 patient had better sparing of the parotid glands and temporomandibular joints with IMRT (dose to 50% parotid volume, 57 Gy, 50 Gy, and 31 Gy, respectively). In the T2bN2M0 patient, the dose to 95% volume of the planning target volume improved from 57.5 Gy in 2D-RT to 64.8 Gy in 3D-CRT and 68 Gy in IMRT. In the T4N2M0 patient, improvement in both target coverage and brainstem/temporal lobe sparing was seen with IMRT planning. In the dose-escalation study for locally advanced disease, IMRT 66 Gy plus 14 Gy 3D-CRT boost achieved an improvement in the therapeutic ratio by delivering a higher dose to the target while keeping the normal organs below the maximal tolerance dose. CONCLUSIONS: IMRT is useful in treating all stages of nonmetastatic nasopharyngeal carcinoma because of its dosimetric advantages. In early-stage disease, it provides better parotid gland sparing. In locally advanced disease, IMRT offers better tumor coverage and normal organ sparing and allows room for dose escalation.     

Combined photon and electron three-dimensional conformal versus intensity-modulated radiotherapy with integrated boost for adjuvant treatment of malignant pleural mesothelioma after pleuropneumonectomy

PURPOSE: The optimal technique for postoperative radiotherapy (RT) after extrapleural pleuropneumonectomy (EPP) of malignant pleural mesothelioma (MPM) remains debated. METHODS AND MATERIALS: The data from 8 right-sided and 9 left-sided consecutive cases of MPM treated with RT after radical EPP were reviewed. Of the 17 patients, 8 had been treated with three-dimensional (3D) conformal RT (3D-CRT) and 9 with intensity-modulated RT (IMRT) with 6-MV photons. The clinical outcome and adverse events were assessed. For comparative planning, each case was replanned with 3D-CRT using photons and electrons or with IMRT. Homogeneity, doses to the organs at risk, and target volume coverage were analyzed. RESULTS: Both techniques yielded acceptable plans. The dose coverage and homogeneity of IMRT increased by 7.7% for the first planning target volume and 9.7% for the second planning target volume, ensuring >or=95% of the prescribed dose compared with 3D-CRT (p < 0.01). Compared with 3D-CRT, IMRT increased the dose to the contralateral lung, with an increase in the mean lung dose of 7.8 Gy and an increase in the volume receiving 13 Gy and 20 Gy by 20.5% and 7.2%, respectively (p < 0.01). A negligible dose increase to the contralateral kidney and liver was observed. No differences were seen for the spinal cord and ipsilateral kidney. Two adverse events of clinical relevant lung toxicity were observed with IMRT. CONCLUSION: Intensity-modulated RT and 3D-CRT are both suitable for adjuvant RT. IMRT improves the planning target volume coverage but delivered greater doses to the organs at risk. Rigid dose constraints for the lung should be respected.     

宫颈癌术后快速旋转调强放疗和三维适形放疗计划的对比研究

目的 探讨宫颈癌术后快速旋转调强放疗（RapidArc）和三维适形放疗（3D-CRT）计划靶区及其周围危及器官（OAR）受照剂量的差异。方法 随机选择10 例宫颈癌术后患者,进行CT 扫描、靶区（PTV）和OAR的勾画,处方剂量50Gy。分别进行RapidArc和3D-CRT计划设计,计算并比较两种计划的PTV剂量均匀度指数（HI）、适形度指数（CI）、最大受照剂量（PTV Dmax）、最小受照剂量（PTV Dmin）、平均受照剂量（PTV Dmean）和OAR受照体积。结果 RapidArc计划的CI及PTV Dmean均优于3D-CRT计划;RapidArc计划对OAR（膀胱V50,直肠V40、V50,左、右股骨头V20）的保护优于3D-CRT计划（P＜0.05）。两种计划的PTV Dmax、PTV Dmin、HI和OAR受照体积（小肠V10、V20、V30、V40、V50,直肠V10、V20、V30, 膀胱V10、V20、V30、V40,左、右股骨头V10、V30、V40、V50）的差异均无统计学意义（P＞0.05）。结论 宫颈癌术后辅助放疗中,RapidArc计划在靶区CI和PTV Dmean方面均优于3D-CRT,同时RapidArc计划在正常组织保护上也有一定的优势。     

子宫颈癌术后盆腔转移三维适形与调强放疗剂量学对比研究

目的 比较三维适形放疗(3DCRT)和调强放疗(IMRT)在子宫颈癌术后盆腔转移病灶靶区(PTY)剂量覆盖和危及器官(OAR)保护方面的差异,探讨子宫颈癌术后盆腔转移病灶的最佳治疗方案.方法 选择10例子宫颈癌根治术后盆腔转移患者,行CT模拟定位后将数据上传至Varian三维计划系统,勾画靶区,进行放疗计划设计后做下列研究:3DCRT计划与IMRT计划对计划靶区PTV的影响及比较;3DCRT计划与IMRT计划中危及器官受最比较分析.结果 采用95%可信区间,CTV至PTV的外放边界定为1 cm.3DCRT计划中3、4、5和6个射野下PTV适形指数分别为0.46、0.67、0.68、0.68,4个以上射野数日的增加不再显著改善靶区分布和减少正常组织受照射体积百分比.IMRT计划中5、7、9、11和13个射野下PTV适形指数分别为0.75、0.83、0.84、0.85、0.85,9个以上射野数目增加不再显著改善靶区分布和减少正常组织受照体积百分比.比较OAR最高照射剂量,IMRT计划中小肠脊髓的最高照射剂量低于3DCRT,直肠膀胱及股骨头的最大剂量差异无统计学意义.结论 子宫颈癌术后盆腔转移放疗者3DCRT以4个射野数计划为优,IMRT以9个射野数计划为优.高剂量范围内IMRT较3DCRT对脊髓及小肠的保护作用明显,IMRT较3DCRT减少了高剂量区直肠、膀胱的受照体积,从而有望减少OAR放射治疗并发症的发生概率.

Abstract：

Objective To compare the differences of target-volume(PTV) coverage and organ at risk (OAR) protection between three dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy(IMRT) for patients with pelvis metastasis of cervical cancer underwent radical hysterectomy and pelvic lymphadenectomy. To explore the optimal treatment methods for pelvis metastasis of cervical cancer.Methods 10 patients with pelvis metastasis of cervical cancer underwent radical hysterectomy and pelvic lymphadenectomy were selected for this study. The images scanned by CT were transferred to treatment planning system to generate 3DCRT and IMRT plans. The impacts of 3DCRT on PTV were compared with those of IMRT. Isodose line and dose volume histograms(DVH) were used to evaluate to the dose-distribution in PTV and OAR. Results For 95 % confidence interval, the margin from CTV to PTV was 1 cm. Conformal indexs (CIs) of PTV for 3, 4, 5 and 6 fields 3DCRT were 0.46, 0.67, 0.68 and 0.68, respectively. When beyond 4 fields, the advantage of adding fields was not significant. CIs of PTV for 5, 7, 9, 11 and 13 fields IMRT were 0.75, 0.83 0.84, 0.85 and 0.85, respectively. When beyond 9 fields, the advantage of adding fields was not significant. The maximum dose of the bowl and spine cord in IMRT plans were lower than that in the 3DCRT plans (P <0.05). Maximum dose of OAR had no significant differences (includingt the bone, recttum and bladder) between IMRT and 3DCRT plans. Conclusion For patients with pelvis metastasis of cervical cancer after radical surgery, 4 fields planning in 3DCRT and 9 fields planning in IMRT are feasible. At high dose levels, the IMRT plans can more significantly protect the bowl and spine cord and decrease the radiation volume of colorectal and urinary bladder at risk than 3DCRT, so IMRT may potentially diminish probability of the normal tissue complications.     

胸上段食管癌三维适形和调强放疗剂量学对比研究

目的 筛选胸上段食管癌不同适形和调强放疗计划优选方案.方法 8例胸上段食管癌cT模拟后参考食管钡餐造影和食管镜结果勾画GTV,按统一标准外扩CTV和PTV,实施3、4、6个野适形治疗计划和3、4、5、7、9、11个野IMRT计划和s-IMRT计划,以95%PTV体积获得6000 cGy处方剂量进行归一,分析各治疗计划靶区剂量分布和危及器官受量,进行剂量学对比研究.结果 3套适形计划之间,PTV剂量参数和体积参数均相近(P＞0.05);6个野适形计划全肺V20高于4个野(P＜0.05),3、6个野适形计划MLD也高于4个野(P＜0.05).6套调强治疗计划中,3个野IMRT计划PTV D100低于9、11个野IMRT计划(P＜0.05);4个野IMRT计划IV高于9、11个野IMRT计划(P＜0.05);9、11个野IMRT计划PTV适形指数CI、剂量参数D95、体积参数V100和V95较57个野IMRT和s-IMRT计划无明显优势(P＞0.05);各IMRT计划之间危及器官受量相近(P＞0.05).胸上段食管癌4个野适形计划PTV CI、PTV剂量参数和体积参数均低于5、7个野IMRT计划和s-IMRT计划(P＜0.05);4个野适形计划全肺V20均高于5、7个野IMRT计划和s-IMRT计划(P＜0.05).结论 胸上段食管癌三维适形放疗中4个野适形计划可为优选方案,调强放疗中5、7个野IMRT计划和s-IMRT计划可为优选方案.胸上段食管癌5、7个野IMRT计划和s-IMRT计划优于4个野适形计划.     

Intensity-modulated radiotherapy for lymphoma involving the mediastinum

PURPOSE: To determine the feasibility, potential advantage, and indications for intensity-modulated radiotherapy (IMRT) in the treatment of Hodgkin's lymphoma or non-Hodgkin's lymphoma involving excessively large mediastinal disease volumes or requiring repeat RT. METHODS AND MATERIALS: Sixteen patients with Hodgkin's lymphoma (n = 11) or non-Hodgkin's lymphoma (n = 5) undergoing primary radiotherapy or repeat RT delivered via an IMRT plan were studied. The indications for using an IMRT plan were previous mediastinal RT (n = 5) or extremely large mediastinal treatment volumes (n = 11). For each patient, IMRT, conventional parallel-opposed (AP-PA), and three-dimensional conformal (3D-CRT) plans were designed using 6-MV X-rays to deliver doses ranging from 18 to 45 Gy (median, 36 Gy). The plans were compared with regard to dose-volume parameters. The IMRT/AP-PA and IMRT/3D-CRT ratios were calculated for each parameter. RESULTS: For all patients, the mean lung dose was reduced using IMRT, on average, by 12% compared with AP-PA and 14% compared with 3D-CRT. The planning target volume coverage was also improved using IMRT compared with AP-PA but was not different from the planning target volume coverage obtained with 3D-CRT. CONCLUSION: In selected patients with Hodgkin's lymphoma and non-Hodgkin's lymphoma involving the mediastinum, IMRT provides improved planning target volume coverage and reduces pulmonary toxicity parameters. It is feasible for RT of large treatment volumes and allows repeat RT of relapsed disease without exceeding cord tolerance. Additional follow-up is necessary to determine whether improvements in dose delivery affect long-term morbidity and disease control.     

Dosimetric evaluation of an ipsilateral intensity modulated radiotherapy beam arrangement for parotid malignancies

Background

We conducted a dosimetric comparison of an ipsilateral beam arrangement for intensity modulated radiotherapy (IMRT) with off-axis beams.

Patients and methods

Six patients who received post-operative radiotherapy (RT) for parotid malignancies were used in this dosimetric study. Four treatment plans were created for each CT data set (24 plans): 1) ipsilateral 4-field off-axis IMRT (4fld-OA), 2) conventional wedge pair (WP), 3) 7 field co-planar IMRT (7fld), and 4) ipsilateral co-planar 4-field quartet IMRT (4fld-CP). Dose, volume statistics for the planning target volumes (PTVs) and planning risk volumes (PRVs) were compared for the four treatment techniques.

Results

Wedge pair plans inadequately covered the deep aspect of the PTV. The 7-field IMRT plans delivered the largest low dose volumes to normal tissues. Mean dose to the contralateral parotid was highest for 7 field IMRT. Mean dose to the contralateral submandibular gland was highest for 7 field IMRT and WP. 7 field IMRT plans had the highest dose to the oral cavity. The mean doses to the brainstem, spinal cord, ipsilateral temporal lobe, cerrebellum and ipsilateral cochlea were similar among the four techniques.

Conclusions

For postoperative treatment of the parotid bed, 4-field ipsilateral IMRT techniques provided excellent coverage while maximally sparing the contralateral parotid gland and submandibular gland.     

Intensity-modulated radiotherapy in patients with locally advanced rectal cancer reduces volume of bowel treated to high dose levels

PURPOSE: To investigate the potential for intensity-modulated radiotherapy (IMRT) to spare the bowel in rectal tumors. METHODS AND MATERIALS: The targets (pelvic nodal and rectal volumes), bowel, and bladder were outlined in 5 patients. All had conventional, three-dimensional conformal RT and forward-planned multisegment three-field IMRT plans compared with inverse-planned simultaneous integrated boost nine-field equally spaced IMRT plans. Equally spaced seven-field and five-field and five-field, customized, segmented IMRT plans were also evaluated. RESULTS: Ninety-five percent of the prescribed dose covered at least 95% of both planning target volumes using all but the conventional plan (mean primary and pelvic planning target volume receiving 95% of the prescribed dose was 32.8 +/- 13.7 Gy and 23.7 +/- 4.87 Gy, respectively), reflecting a significant lack of coverage. The three-field forward planned IMRT plans reduced the volume of bowel irradiated to 45 Gy and 50 Gy by 26% +/- 16% and 42% +/- 27% compared with three-dimensional conformal RT. Additional reductions to 69 +/- 51 cm(3) to 45 Gy and 20 +/- 21 cm(3) to 50 Gy were obtained with the nine-field equally spaced IMRT plans-64% +/- 11% and 64% +/- 20% reductions compared with three-dimensional conformal RT. Reducing the number of beams and customizing the angles for the five-field equally spaced IMRT plan did not significantly reduce bowel sparing. CONCLUSION: The bowel volume irradiated to 45 Gy and 50 Gy was significantly reduced with IMRT, which could potentially lead to less bowel toxicity. Reducing the number of beams did not reduce bowel sparing and the five-field customized segmented IMRT plan is a reasonable technique to be tested in clinical trials.     

Dosimetric comparisons of helical tomotherapy and step-and-shoot intensity-modulated radiotherapy in nasopharyngeal carcinoma

PURPOSE: The study evaluates and quantifies the potential dosimetric gains of helical tomotherapy (HT) versus step-and-shoot intensity-modulated radiotherapy (SaS-IMRT) for nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS: Twenty consecutive NPC patients curatively treated by HT were examined. Each case was planned by HT and SaS-IMRT (ADAC Pinnacle(3)) planning system, respectively. Dose plans were compared using dose volume histograms (DVH), conformity index (CI), homogeneity index (HI), and minimal dose to 1cc (D(min_1cc)) of the planned target volume (PTV) and a comprehensive quality index (CQI) of ten organs at risk (OARs). The prescribed dose/fractionation was 72Gy to the PTV, 64.8Gy to the elective PTV, and 54Gy to the clinically negative neck region. The plan of 54Gy to the PTV (PTV(54)) was used to evaluate the CI and HI in the target. The cumulative doses of the three PTV plans to the OARs were calculated. RESULTS: We observed the HT plans significantly improved the CI (improvement ratio: 11.9+/-5.5%) and HI (improvement ratio: 8.8+/-1.5%) of the PTV(54) compared with SaS-IMRT plans. In addition, the mean/maximal dose of most of the OARs except chiasm was significantly reduced in HT plans, with the CQI of 0.92+/-0.08. A negative result of HT in chiasm was observed but only significantly revealed in cases without skull base infiltration. CONCLUSIONS: A dosimetric gain in CI and HI of PTV and sparing of OARs was significantly obtained in HT versus SaS-IMRT plans in NPC patients. Whether such dosimetric superiority in HT could transfer into clinical advantages needs further investigation.