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Objective@#To develop and evaluate an automatic intensity-modulated radiation therapy (IMRT) program for cervical cancer based on a database of overlap volume histogram (OVH) and high-quality cervical IMRT plans for previously-treated patients.@*Methods@#A database consisting of high-quality IMRT plans and OVHs from 200 cervical cancer patients was established. OVHs of another 26 cervical cancer patients were converted into gray level images to calculate the image similarity compared with those from the database. The planning optimization function of the patients from the database with the highest image similarity was selected and inherent Pinnacle3 scripts were utilized to automatically generate IMRT plan. Finally, the dosimetric parameters, plan quality and design time were statistically compared between the automatic and manual plans.@*Results@#The target coverage, conformity index and homogeneity index did not significantly differ between two plans (all P>0.05). The V40, V45 and mean dose for the rectum in the automatic plans were significantly decreased by 6.1%, 1.3% and 50.7 cGy than those in the manual plans (all P<0.05). Compared with the manual plans, the mean dose for the intestine and femur in the automatic plans were significantly reduced by 31.7 cGy and 188.9 cGy (both P<0.05), whereas the mean dose for the ilium was slightly decreased by 92.3 cGy in the automatic plans (P>0.05). The plan design time was shortened by 71% in the automatic plans.@*Conclusions@#The automatic IMRT plans based on a database of OVH and high-quality IMRT plans can not only significantly shorten the plan design time, but also reduce the irradiated dose of normal tissues without compromising the target coverage and conformity index.
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Objective To develop and evaluate an automatic intensity-modulated radiation therapy (IMRT) program for cervical cancer based on a database of overlap volume histogram (OVH) and high-quality cervical IMRT plans for previously-treated patients.Methods A database consisting of high-quality IMRT plans and OVHs from 200 cervical cancer patients was established.OVHs of another 26 cervical cancer patients were converted into gray level images to calculate the image similarity compared with those from the database.The planning optimization function of the patients from the database with the highest image similarity was selected and inherent Pinnacle3 scripts were utilized to automatically generate IMRT plan.Finally,the dosimetric parameters,plan quality and design time were statistically compared between the automatic and manual plans.Results The target coverage,conformity index and homogeneity index did not significantly differ between two plans (all P＞0.05).The V40,V45 and mean dose for the rectum in the automatic plans were significantly decreased by 6.1％,1.3％ and 50.7 cGy than those in the manual plans (all P＜0.05).Compared with the manual plans,the mean dose for the intestine and femur in the automatic plans were significantly reduced by 31.7 cGy and 188.9 cGy (both P＜0.05),whereas the mean dose for the ilium was slightly decreased by 92.3 cGy in the automatic plans (P＞ 0.05).The plan design time was shortened by 71％ in the automatic plans.Conclusions The automatic IMRT plans based on a database of OVH and high-quality IMRT plans can not only significantly shorten the plan design time,but also reduce the irradiated dose of normal tissues without compromising the target coverage and conformity index.
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Objective To investigate the precision of full six-degree target shift corrections using the ArcCHECK system.Metbods Fourteen patients receiving intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) in Fujian Medical University Cancer Hospital from May to September,2015 were selected.The first treatment setup errors were obtained using cone-beam computed tomography.The setup errors were simulated in ArcCHECK,and the full six-degree target shift corrections was used to correct the errors.The plans without and with setup errors and the plan with corrected setup errors were taken.The paired t-test was used to compare dose to agreement (DTA) and Gamma passing rates between the plan without setup errors and the plan with setup errors and plan with corrected setup errors.Results The DTA and Gamma passing rates were (96.76± 1.57)％ and (98.35±0.92)％ for the plan without setup errors,(59± 21.42) ％ and (62.86± 21.63) ％ for the plan with setup errors,and (91.41± 4.82) ％ and (94.11±4.33)％ for the plan with corrected setup errors.There were significant differences between the plan without setup errors and the plan with setup errors and plan with corrected setup errors in DTA passing rate (t=6.64 and 5.13,both P＜0.05) and Gamma passing rate (t=6.15 and 4.19,both P＜0.05).Conclusions The full six-degree target shift corrections can be used in IMRT for NPC,with good results in correcting setup errors and improving the precision for IMRT dose distribution.
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Objective To compare and analyze the dosimetric discrepancy of combind intracavitary/interstitial brachytherapy using three different kinds of optimization method in locally advanced cervical cancer.Methods Totally 20 cases of locally advanced cervical cancer were selected and divided into three groups according to different optimization method which include manual optimization group (MO) based on graphical optimization,inverse planning simulated annealing (IPSA 1)based on simulated annealing optimization algorithm,IPSA 2 based on IPSA 1 with limitation on maximum dose of target.The dose volume histogram parameters of the targets (V200,V150,V100,D100,D90,HI) and the OARs(D0.1 cm3,D1 cm3 and D2 cm3) were analyzed.Results For CTV,compared with MO,there was no significantly statistical difference in D100between IPSA 1 and IPSA 2(P ＞ 0.05).However,V200,V150,V100 and HI for ISPA1 were better than for ISPA2 (t =-3.422-9.910,P ＜ 0.05).In addition,V100 and D100 in ISPA1 were better than in ISPA2 (t =7.238,5.032,P ＜0.05).For OARs,D0.1 cm3,D1 cm3 and D2 cm3 in rectum,bladder,sigmoid colon of both ISPA 1 and ISPA 2 were dramatically lower than those of MO (t =2.235 5.819,P ＜ 0.05),without significantly statistical difference found between ISPA1 and ISPA2.Conclusions For combined intracavitary/interstitial brachytherapy in locally advanced cervical cancer,all treatment plans based on three different kinds of optimization methods can meet the clinical need.Moreover,inverse optimization can ensure dose coverage over target and reduce maximum dose of rectum,bladder and sigmoid colon.
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Objective To compare the dosimetric difference among plans designed by 4-field,6-field TomoDirect and TomoHelical techniques in Tomotherapy system for left-breast cancer patients with radiotherapy after breast-conserving surgery.Method A total of 16 patients with left-breast cancer following breast-conserving surgery and intensity-modulated radiation therapy were enrolled in this retrospective study.The 4-field TomoDirect (TD4),6-field TomoDirect (TD6),and TomoHelical (TH) techniques were applied to design simulation plans in tomotherapy system for each patient,respectively.The differences of dose distribution and treatment parameters were analyzed in this study.Results Three plans all met the clinical requirement.Thereinto,TD4 was superior to TH in the dose limitation of organs at risk (OARs),especially the max dose of cord and right-breast,thc 5 Gy radiation volume of lung,and the mean dose of heart(F =595.60,129.24,60.44,65.37,P ＜ 0.05),but inferior to TH in dose homogeneity (HI) and conformity (CI) (F =2.78,60.93,P ＜ 0.05).However,TD6 improved TD4's HI and CI when delivered the lower OARs dose compared to TH.Meanwhile,the number of monitor units was less in TD technique and reduced the treatment times (F =24.89,3.75,P ＜ O.05).Conclusions For the radiotherapy of left-breast cancer patients after breast-conserving surgery,TD6 technique appeared to be superior,with the lower radiation dose of OARs compared to TH technique,and the better target's HI and CI in comparison with TD4 technique,especially in patients with early stage breast cancer.
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Objective To investigate the changes in volume and spatial location of target areas and normal tissues before and during intensity?modulated radiotherapy (IMRT) for cervical cancer by quantitative means. Methods Forty patients with cervical cancer who were treated with IMRT were enrolled as subjects. Computed tomography ( CT) was performed before IMRT and during IMRT when a dose of 27 Gy ( 15 fractions) was reached. Clinicians delineated the target areas and organs at risk in the two groups of CT images. The target areas and organs at risk in one group of images were mapped to the other group of CT image by image registration using the Pinnacle treatment planning system. Volume changes in target areas and organs at risk were analyzed, and changes in the spatial location were evaluated by volume difference method and Dice similarity method. Comparison was made by paired t?test. Results There were significant differences in gross target volumes of primary tumor lesions ( GTV?T) and pelvic metastatic lymph nodes (GTV?N) before and during IMRT ( P= 0?? 000; P= 0?? 000). According to the evaluation by volume difference method, the average rate of change in GTV?T was (38.64±19?? 50)% with a range between 3?? 16%and 86?? 49%, while the average rate of change in GTV?N was (42.49± 25?? 68)% with a range between 2?? 79% and 87?? 42%. In the organs at risk, the bladder had the maximum rate of volume change, the average of which was (55.13±33?? 40)% with a range between 3?? 25% and 116?? 01%. According to the evaluation by Dice similarity method, the average Dice similarity coefficient for GTV?T was 0.50± 0?? 18 with a range between 0?? 10 and 0?? 85, while the average Dice similarity coefficient for GTV?N was 0.31±0?? 20 with a range between 0?? 00 and 0?? 71. The rectum had the minimum Dice coefficient in the organs at risk, the average of which was 0.57± 0?? 14 with a range between 0?? 18 and 0?? 76 . Conclusions For patients with cervical cancer to receive IMRT, since there are substantial changes in volume and spatial location of target areas and normal tissues before and during treatment, it is quite necessary to modify the treatment regimen in time in order to provide adequate doses for target areas and avoid overdose for organs at risk.
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Objective To investigate change of the volume and the epicenter of target volume under different scan speed of the three-dimensional (3D) simulation computed tomography (CT) and determine the scan speed which close to ITV.Methods A dynamic phantom-QUASAR,with a 3 cm × 3 cm × 3 cm target cubic simulating respiratory motion was used.The phantom was set with three different amplitudes and breathing frequencies under different scan speed.The dynamic phantom was also scanned using simulation 4DCT as ITV was the standard.The length of the phantom was 12 cm,the scan time were 6.6 s,12.8 s,31.7 s.The volume and epicenter of the target identified from 3DCT images were calculated and compared to 4DCT images.The number of times of target length (30 ± 2) mm/total scan times was used to assese the accuracy.Results The total accuracy was 6.8％.For different scan speed,the accuracy were 13％,4％ and 2％,respectively.The length of the epicenter of the target volume was (318.9 ±0.37) mm,(683.2 ±0.44) mm,(682.9 ± 0.66) mm under the 0.5 cm,1.0 cm and 2.0 cm,respectively.When the scan time was 31.7 s,the volume of the target from the 3DCT were close to ITV-10 mm,the frequency were 50％,78％,56％ for three different amplitude.Conclusions This study shows that the images from the 3D simulation CT were the partial image of the breathing cycle,and the epicenters were diversed with the breathing amplitude and scan speed.The accuracy rate of the 3DCT reflects the real target is low.In addition,the epicenter of the target changed randomly.
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Objective To compare the dosimetric differences of fixed field intensity-modulated radiation therapy(IMRT),volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) for nasopharyngeal carcinoma (NPC) patients.Methods Eighteen NPC patients previously treated with VMAT were retrospectively included and re-planned using HT and IMRT (7 fields) techniques utilizing the same dose prescription and optimization objectives.The following parameters were compared across the three types of plans:homogeneity index (HI),conformity index (CI),maximum dose (Dmax) and mean dose (Dmean) of targets ; the Dmax and Dmean of organs at risk (OARs) ; the doses and volumes of volume of interest; the treatment delivery time and monitor units (MU).Results Clinically acceptable target coverage could be achieved by IMRT,VMAT and HT plans.The HT plans were the best yet IMRT plans were the worst in HI and CI of targets.IMRT imposed highest doses to OARs while HT deposited least doses to the spinal cord,brainstem and parotid.However,the VMAT plans displayed the lowest doses on optic nerves,chiasma and lens while highest doses were found in IMRT plans.The average delivery time per fraction of IMRT (8.0±0.5) min were more than that of HT (7.4 ±0.9) min and VMAT (3.9 ±0.1) min plans.The MUs of IMRT plans (711.4 ±78.7) were larger than that of VMAT plans (596.4 ±33.7).Conclusions Three types of plans can all achieve the clinical dosimetric demands,but HT has the best performance on CI and HI.VMAT is most efficient regarding the delivery time and total MUs.
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Cone-beam CT (CBCT) of Elekta can be used to analyze the setup errors in intensity modulated radiotherapy. A total of 240 patients with head and neck cancer were chosen in the period from October, 2009 to October, 2010. Their CBCT images were obtained after initial setup, and registered to the planning CT images, and then the setup errors on translational directions (X, Y, Z) and on rotational directions (U, V, W) were obtained and analyzed. The results showed that the setup errors on translational directions in Y-axis and Z-axis were larger than in X-axis, and the setup errors on rotational directions in Y-axis was much more obvious than those on the other two directions, which should be taken care during the patient daily setup. It may be concluded that the CBCT system can improve the precision for radiotherapy.
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Humans , Cone-Beam Computed Tomography , Methods , Head and Neck Neoplasms , Diagnostic Imaging , Radiotherapy , Radiotherapy Setup Errors , Radiotherapy, Intensity-ModulatedABSTRACT
Objective To evaluate the dosimetric characteristics of hippocampal formation (HF) in the intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC).Methods Fifty-nine NPC patients underwent IMRT.Simultaneous integrated boost technology was used to determine the doses for the target areas.The dose ranges of the HF were collected by dose-volume histogram.The influence of T stage on the exposure doses ( Dmax,Dmean,D20,V10,V20,V30,and V40 ) were compared.Results The maximum dose for the HF (Dmax) ranged from 11.1 to 78.2 Gy(F =24.2,P ＜0.05) and the Dmean ranged from 3.2 to 44.6 Gy ( F =16.3,P ＜ 0.05 ).The Dmax and Dmean of the T1-2 stage patients were (40.8 ±9.4) Gy and ( 12.5 ±5.1 ) Gy,respectively,both significantly lower than those of the T3-4 stage patients [ (58.6± 14.8) Gy,(20.9± 9.3 ) Gy].The mean exposed volume of the T4 stage patients was significantly larger than that of the T1 and T2 stages patients.Conclusions In the IMRT of NPC,the HF receives rather high irradiation dose.T stage is the main factor influencing the dose,especially T3 and T4 stages deserve serious attention.
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Objective To investigate the dosimetric performance of COMPASS system,a novel 3D quality assurance system for the verification of nasopharyngeal carcinoma volumetric modulated therapy (VMAT) treatment plan.Methods Eight VMAT treatment plans of nasopharyngeal carcinoma patients were performed with MasterPlan,a treatment planning system (TPS),and then these treatment plans were sent to the COMPASS and MOSAIQ system,a coherent control system,respectively.Comparison of the COMPASS reconstructed dose versus TPS dose was conducted by using the dose volume-based indices:dose received by 95％ volume of target ( D95％ ),mean dose ( Dmean ) and γ pass rate,dose to the 1％ of the spinal cord and brain stem volume ( D1％ ),mean dose of leaf and right parotid ( Dmean ),and the volume received 30 Gy for left and right parotid (V30).COMPASS can reconstruct dose with the real measured delivery fluence after detector commissioning.Results The average dose difference for the target volumes was within 1％,the difference for D95 was within 3％ for most treatment plans,and the γ pass rate was higher than 95％ for all target volumes.The average differences for the D1％ values of spinal cord and brain stem were ( 4.3 ± 3.0) ％ and ( 5.9± 2.9 ) ％ respectively,and the average differences for the Dmean values of spinal cord and brain stem were ( 5.3 ± 3.0 ) ％ and ( 8.0 ± 3.5 ) ％ respectively.In general the COMPASS measured doses were all smaller than the TPS calculated doses for these two organs.The average differences of the Dmean values of the left and right parotids were( 6.1± 3.1 ) ％ and ( 4.7 ± 4.4 ) ％ respectively,and the average differences of the V30 values of the left and right parotids were (9.4 ± 7.5 ) ％ and (9.4 ± 9.9)％ respectively.Conclusions An ideal tool for the VMAT verification,the patient anatomy based COMPASS 3D dose verification system can check the dose difference between the real delivery and TPS calculation directly for each individual organ,either target volumes or critical organs.
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ObjectiveTo analyze the correlation between primary tumor volume (PTV) and prognosis of nasopharyngeal carcinoma ( NPC ) treated by intensity-modulated radiotherapy ( IMRT ).Methods330 NPC patients treated by IMRT were included.Pretreatment computerized tomography image were input into tree-dimensional treatment-planning system,in which the primary tumor volume were calculated automatically.The receiver operating characteristic curve was used to determine the best cut-off point of PTV.Within the framework of UICC 2002 T stage,The PTV was divided into four groups:V1 ＜ 10cm3,V2 10-25 cm3,V3 ＞ 25-50 cm3 and V4 ＞ 50 cm3.Kaplan-Meier and Logrank test was used to analyze the survival,Cox proportion risk regression model were used to analysis the correlation between PTV and prognosis.ResultsThe mean PTV for all NPC patients was ( 34.2 ± 27.1 ) cm3 with the range of 0.4- 153.7 cm3.The 3-year overall survival for V1,V2,V3 and V4 stage were 88.6％,90.0％,91.2％ and 74.2％,respectively (x2 =12.83,P =0.005 ).There was no significant difference among V1,V2 and V3in terms of overall survival ( x2 =1.96,P =0.376).The 3-year distant metastasis-free survival and diseasesfree survival or overall survival were decrease in PTV ＞50 cm3 and PTV≤50 cm3 (77.4％:89.9％,x2 =7.24,P=0.007and 64.5％:85.1％,x2 =13.95,P=0.000 or 74.2％:90.3％,x2 =11.76,P=0.001).Multivariate analysis revealed that PTV was a adverse prognostic factors for overall survival (x2 =0.00,P =2.580).ConclusionOur data showed that the primary tumor volume had significantly impacted on the prognosis of NPC patients treated by intensity modulated radiotherapy.
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Objective To measure the set-up errors of patients with head and neck (H&N) cancer during the image guided intensity-modulated radiotherapy (IMRT) treatment and analyze the impact of setup errors on dose distribution ; then to further investigate the necessity of adjustment online for H&N cancer during IMRT treatment.Methods Cone-beam CT (CBCT) scanning of thirty patients with H&N cancer were acquired by once weekly with a total of 6 times during IMRT treatment.The CBCT images and the original planning CT images were matched by the bony structure and worked out the translational errors of the x,y,z axis,as well as rotational errors.The dose distributions were recalculated based on the data of each setup error.The dose of planning target volume (PTV) and organs at risk were calculated in the replanning,and than compared with the original plan by paired t-test.Results The mean value of x,y,z axis translational set-up errors were ( 1.06 ± 0.95 ) mm,( 0.95 ± 0.77 ) mm and ( 1.31 ± 1.07 ) mm,respectively.The rotational error of x,y,z axis were ( 1.04 ±0.791 ),( 1.06 ±0.89) and (0.81 ±0.61 ),respectively.PTV 95％ volume dose ( D95 ) and PTV minimal dose of replanning for 6 times set-up were lower than original plan (6526.6 cGy:6630.3 cGy,t =3.98,P =0.000 and 5632.6 cGy:5792.5 cGy,t =- 2.89,P =0.007).Brain stem received 45 Gydose volume ( V45 ) and 1％ brain stem volume dose ( D01 )were higher than original plan ( 3.54％:2.75％,t =3.84,P =0.001 and 5129.7 cGy:4919.3 cGy,t =4.36,P =0.000).Conclusions The set-up errors led to the dose of PTV D95 obviously insufficient and significantly increased V45,D01 of the brainstem.So,adjustment online is necessary for H&N cancer during IMRT treatment.
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Objective To study the feasibility of dose calculation using kilovoltage X-ray cone-beam CT (KVCBCT) imaging for head-and-neck radiation therapy.Methods 11 patients with nasopharyngeal carcinoma were scanned with KVCBCT to adjust position before treatment, and rescanning images with KVCBCT after correction were input a treatment-planning system.The dose was recalculated by applying the patients′ treatment plans based on planning CT to the KVCBCT images.The dose distributions and dose volume histograms (DVH) of the tumor and critical structures were compared with the original treatment plan.Results The DVH and dose distribution of the plan based on the KVCBCT are compared with that of the planning CT, and they shows a good consistency for the 11 cases.The doses calculated from the planning CT and KVCBCT were compared on the isocenter planes.Using γ analysis with a criterion of 3%/3 mm, 98.0%±1.33% of the points on the isocenter planes in the planning CT and KVCBCT.The difference of the dose to target volume was<1% and to normal structure was<2%.Conclusions This study indicated that CBCT images can be used to make a treatment plan with its individual hounsfield unit-electron density calibration curve.
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Objective To characterize angular dependency of MatfiXX and develop a method for its calibration in order to verify treatment plan with original gantry angles.Methods Absolute dose calibration was carried with thimble ionization chamber on the linear accelerator.so as to make sure 1 MU=1 cGy at the depth of maximum dose(dmax).A MatriXX was put into a Mutlicube phantom,and the ionization chamber matrix was calibrated with absolute dose.In order to determine a correction factor CF as a function of gantry angle θ.open beam fields of 10 cm×10 cm size were irradiated for gantry angles θ=0°-180°(every 5°)and every 1°for lateral angles θ in the range of 85°-95°.CF was defined as the ratio of the dose measured with ionization chamber and the dose from MatriXX.Results Relatively large discrepancies in response to posterior VS.anterior fields for MatriXX detectors(up to 10%)were found during the experiment and relatively large variability of response as a function of gantry angle.The pass rate of treatment plan in lateral beams was lower than that of other beams.The isodose distribution of corrected MatriXX matched well with the outcome from the treatment planning system. Conclusions The angular dose dependency of MatriXX must be considered when it is used to verify the treatment plan with original gantry angles.
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Objective To evaluate the impact of reducing clinical target volume (CTV) on the efficacy of intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC) . Methods Between August 2003 and March 2007, 380 NPC patients were treated with IMRT with reduced CTV.CTV1, defined as high risk region, included GTV +5 - 10 mm margin and the entire nasopharyngeal mucosa +5 mm submucosal volume; CTV2, designed for potentially involved regions, included the nasopharyngeal cavity (limited to the posterior part of nasal cavity only), maxillary sinus (limited to 5 mm anterior to the posterior nasal aperture and maxillary mucosa), pterygopalatine fossa, posterior ethmoid sinus,parapharyngeal space, skull base, anterior third of clivus and cervical vertebra, inferior spheniod sinus and cavernous sinus and internal group of retropharyngeal lymph nodal regions from the base of skull to cranial edge of the second cervical vertebra. The prescription dose was: GTV 66. 00 -69. 75 Gy/30 - 33 f, CTV1 60. 00 -66. 65 Gy,CTV2/CTVN 54. 0 -55.8 Gy. 308 patients with stage Ⅲ or Ⅳ diseases also received cisplatin-based neoadjuvant chemotherapy. Results The follow-up rate was 100%. 145 patients were followed-up to 3 years. The 3-year estimated local control, regional control, metastasis-free survival,disease-free survival and overall survival rates were 94. 9%, 97.4%, 86. 2%, 80. 9% and 89. 0%,respectively. Multivariate analysis revealed that N-classification was a significant prognostic factor for metastasis-free survival (x2 = 20. 80, P = 0. 001), N-classification (x2 = 18. 30, P = 0. 003) and age (x2 =7. 31, P =0. 004) were independent prognostic factors for overall survival. Grade 2 xerostomia was observed in 5.6% of the patients after two years of IMRT, no Grade 3 or 4 xerostomia was observed. Local, regional,and distant failures were developed in 4. 2%, 2. 6% and 12. 1% of the patients, respectively. Conclusions The IMRT approach with reduced CTV2 provids a favorable outcome for NPC with acceptable toxicities.