Dosimetric comparison of vaginal vault brachytherapy vs applicator-guided stereotactic body radiotherapy with volumetric modulated arc therapy and helical tomotherapy for endometrium cancer patients

We performed this dosimetric study to compare a nonstandard volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) techniques with high-dose rate (HDR) brachytherapy (BRT) plan of vaginal vault in patients with postoperative endometrial cancer (EC). Twelve postoperative patients with early stage EC were included in this study. Three plans were performed for each patient; dosimetric and radiobiological comparisons were made using dose-volume histograms and equivalent dose for determining the planning target volume (PTV) coverages in brachytherapy and external beam radiotherapy, and organs-at-risk (OARs) doses between three different delivery techniques. All the plans achieved adequate dose coverage for PTV; however, the VMAT plan yielded better dose conformity, and the HT plan showed better homogeneity for target volume. With respect to the OARs, the bladder D_2cc was significantly lower in the BRT plan than in the VMAT and HT plans, with the highest bladder D_2cc value being observed in the HT plan. However, no difference was observed in the rectum D_2cc of the three plans. Other major advantages of the BRT plan over the VMAT and HT plans were the relatively lower body integral doses and femoral head doses as well as the fact that the integral doses were significantly lower in the BRT plan than in the VMAT and HT plans. This is the first dosimetric comparison of vaginal vault treatment for EC with BRT, VMAT, and HT plans. Our analyses showed the feasibility of stereotactic body radiotherapy technique as an alternative to HDR-BRT for postoperative management of EC patients.     

三维适形、逆向调强及旋转调强放疗技术对部分乳腺外照射的剂量学比较

目的 比较三维适形(3 D-CRT)、逆向调强(IMRT)及旋转调强(V-MAT)3种部分乳腺外照射(EB-PBI)治疗计划的剂量学差异.方法 选择定位影像资料完整的12例保乳术后行EB-PBI患者,每例患者分别设计3D-CRT、IMRT、V-MAT 3种治疗计划,比较3种计划的靶区剂量分布、危及器官受照剂量及所需机器跳数(MU)和治疗时间.结果 3D-CRT计划的靶区适形度最差,V-MAT计划的处方剂量靶区覆盖率及靶区剂量均匀性最差.3D-CRT计划中患侧肺V5、V10和平均剂量低,而患侧肺V30高;计划间患侧肺V20差异无统计学意义;V-MAT计划中15、20和25 Gy剂量包绕的同侧正常乳腺体积少;对于心脏V5、平均剂量及最大剂量、对侧肺平均剂量、甲状腺平均和最大剂量,IMRT＞ V-MAT＞ 3D-CRT,计划间两两比较差异均有统计学意义(z=-2.94 ～ -2.09,P＜0.05).3D-CRT、IMRT和V-MAT计划所需MU值分别为417.6 ±34.4、772.8±54.4和631.0±109.0,计划间两两比较差异均有统计学意义(z=-2.93、-2.76、-2.93,P＜0.05);V-MAT计划施照时间短.结论 对于部分乳腺癌的放射治疗,旋转调强计划在降低患侧靶区外正常乳腺组织受照射剂量和减少治疗时间方面优势比较明显.     

宫颈癌术后放疗中自动计划与人工计划的剂量学比较

目的 比较容积弧形调强（VMAT）人工计划与自动计划的剂量学参数,评估自动计划在临床宫颈癌术后放疗应用的可行性以及剂量学特点。方法 选取23例宫颈癌术后病例,其中Ⅱ_A期8例,Ⅱ_B期15例,使用Pinnacle³放射治疗计划系统分别设计人工VMAT和自动VMAT计划。比较两种计划靶区的D_mean、D₉₅、适形指数（CI）、均匀性指数（HI）、危及器官（OAR）的剂量体积直方图（DVH）、平均优化时间、调试次数以及机器跳数（MU）。结果 自动计划得到的靶区D_mean、CI以及HI均优于人工计划（t=4.65~14.92,P<0.05）,而D₉₅无明显差异（P>0.05）;自动计划得到的OAR各参数均优于人工计划（t=3.30~14.42,P<0.05）;自动计划明显减少了计划的平均优化时间（72 min,t=3.85,P<0.05）和调试次数（2次,t=5.41,P<0.05）;自动计划和人工计划的平均机器跳数分别为（819±53）和（638±41） MUs,自动计划跳数增加了181 MUs。结论 使用Pinnacle³自动设计的宫颈癌术后VMAT计划具有临床可行性,并且自动VMAT计划与人工VMAT计划相比提高了计划质量,减少了计划设计时间、人为因素对于计划质量的影响。     

宫颈癌术后容积旋转调强放疗与5野调强放疗计划的剂量学比较

目的比较宫颈癌术后容积旋转调强放疗（VMAT）与5野调强放疗（5F-IMRT）计划的剂量学差异,并在危及器官保护方面进行分析。方法选择10例宫颈癌术后放疗的5F-IMRT计划,按相同的剂量限制对每例患者行单弧VMAT和双弧VMAT计划设计,比较3种计划的靶区剂量、适形度指数、均匀性指数、危及器官剂量及加速器跳数。组间比较采用单因素方差分析检验,组间两两比较采用LSD检验。结果单弧VMAT和双弧VMAT均能满足靶区处方剂量的要求,在靶区最大剂量、平均剂量、适形度指数和均匀性指数上,双弧VMAT与5F-IMRT计划相当,单弧VMAT计划最差,差异有统计学意义（F=24.102、13.710、5.919、11.045,均P < 0.05）;靶区最小剂量比较,3种计划差异无统计学意义（F=3.323,P>0.05）。单弧VMAT和双弧VMAT计划的加速器跳数明显少于5F-IMRT计划,差异有统计学意义（F=295.138,P < 0.05）。对于小肠、直肠和膀胱的参数最大剂量,双弧VMAT与5F-IMRT计划相当,单弧VMAT计划最差,差异有统计学意义（F=16.069、7.521、13.966,均P < 0.05）。对于膀胱的参数V20、V30和V40（V表示受照剂量体积百分比）,5F-IMRT优于单弧VMAT和双弧VMAT,差异有统计学意义（F=5.142、20.095、7.387,均P < 0.05）。对于左股骨头参数V20和V30,单弧和双弧VMAT优于5F-IMRT,差异有统计学意义（F=3.717、16.040,均P < 0.05）。对于右股骨头参数V30和V40,单弧和双弧VMAT优于5F-IMRT,差异有统计学意义（F=10.873、7.791,均P < 0.05）。结论宫颈癌术后放疗,双弧VMAT计划在靶区剂量学参数上与5F-IMRT计划相当,单弧VMAT计划较差。在危及器官保护方面,3种计划各有优势,但VMAT计划的加速器跳数明显减少,可以提高治疗效率,值得进一步研究。     

Dosimetric comparison of helical tomotherapy,volumetric-modulated arc therapy,intensity-modulated radiotherapy,and field-in-field technique for synchronous bilateral breast cancer

Purpose: To compare the dosimetric characteristics of helical tomotherapy (HT), volumetric-modulated arc therapy (VMAT), intensity-modulated radiotherapy (IMRT), and tangential field-in-field technique (FIF) for the treatment of synchronous bilateral breast cancer (SBBC). Methods and Materials: Ten patients with early-stage unilateral breast cancer were selected for simulating the patients with SBBC in this retrospective analysis. Treatment plans with HT, VMAT, IMRT, and FIF were generated for each patient with a total dose of 50.4 Gy in 28 fractions to the target. Plan quality, namely conformity index (CI), homogeneity index (HI), dose-volume statistics of organs at risk (OARs), and beam-on time (BOT), were evaluated. Results: HT plans showed a lower mean heart dose (3.53 ± 0.31Gy) compared with the other plans (VMAT = 5.6 ± 1.36 Gy, IMRT = 3.80 ± 0.76 Gy, and FIF = 4.84 ± 2.13 Gy). Moreover, HT plans showed a significantly lower mean lung dose (p < 0.01) compared with the other plans: mean right lung doses were 6.81 ± 0.67, 10.32 ± 1.04, 9.07 ± 1.21, and 10.03 ± 1.22 Gy and mean left lung doses were 6.33 ± 0.87, 8.82 ± 0.91, 7.84 ± 1.07, and 8.64 ± 0.99 Gy for HT, VMAT, IMRT, and FIF plans, respectively. The mean dose to the left anterior descending artery was significantly lower in HT plans (p < 0.01) than in the other plans: HT = 19.41 ± 0.51 Gy, VMAT = 25.77 ± 7.23 Gy, IMRT = 27.87 ± 6.48 Gy, and FIF = 30.95 ± 10.17 Gy. FIF plans showed a worse CI and HI compared with the other plans. VMAT plans showed shorter BOT (average, 3.9 ± 0.2 minutes) than did HT (average, 11.0 ± 3.0 minutes), IMRT (average, 6.1 ± 0.5 minutes), and FIF (average, 4.6 ± 0.7 minutes) plans. Conclusions: In a dosimetric comparison for SBBC, HT provided the most favorable dose sparing of OARs. However, HT with longer BOT may increase patient discomfort and treatment uncertainty. VMAT enabled shorter BOT with acceptable doses to OARs and had a better CI than did FIF and IMRT.     

Volumetric-modulated arc radiotherapy for pancreatic malignancies: Dosimetric comparison with sliding-window intensity-modulated radiotherapy and 3-dimensional conformal radiotherapy

Volumetric-modulated arc radiotherapy (VMAT) is an iteration of intensity-modulated radiotherapy (IMRT), both of which deliver highly conformal dose distributions. Studies have shown the superiority of VMAT and IMRT in comparison with 3-dimensional conformal radiotherapy (3D-CRT) in planning target volume (PTV) coverage and organs-at-risk (OARs) sparing. This is the first study examining the benefits of VMAT in pancreatic cancer for doses more than 55.8 Gy. A planning study comparing 3D-CRT, IMRT, and VMAT was performed in 20 patients with pancreatic cancer. Treatments were planned for a 25-fraction delivery of 45 Gy to a large field followed by a reduced-volume 8-fraction external beam boost to 59.4 Gy in total. OARs and PTV doses, conformality index (CI) deviations from 1.0, monitor units (MUs) delivered, and isodose volumes were compared. IMRT and VMAT CI deviations from 1.0 for the large-field and the boost plans were equivalent (large field: 0.032 and 0.046, respectively; boost: 0.042 and 0.037, respectively; p > 0.05 for all comparisons). Both IMRT and VMAT CI deviations from 1.0 were statistically superior to 3D-CRT (large field: 0.217, boost: 0.177; p < 0.05 for all comparisons). VMAT showed reduction of the mean dose to the boost PTV (VMAT: 61.4 Gy, IMRT: 62.4 Gy, and 3D-CRT: 62.3 Gy; p < 0.05). The mean number of MUs per fraction was significantly lower for VMAT for both the large-field and the boost plans. VMAT delivery time was less than 3 minutes compared with 8 minutes for IMRT. Although no statistically significant dose reduction to the OARs was identified when comparing VMAT with IMRT, VMAT showed a reduction in the volumes of the 100% isodose line for the large-field plans. Dose escalation to 59.4 Gy in pancreatic cancer is dosimetrically feasible with shorter treatment times, fewer MUs delivered, and comparable CIs for VMAT when compared with IMRT.     

Dosimetric comparison of volumetric modulated arc therapy and intensity-modulated radiation therapy for pancreatic malignancies

Volumetric-modulated arc therapy (VMAT) has been previously evaluated for several tumor sites and has been shown to provide significant dosimetric and delivery benefits when compared with intensity-modulated radiation therapy (IMRT). To date, there have been no published full reports on the benefits of VMAT use in pancreatic patients compared with IMRT. Ten patients with pancreatic malignancies treated with either IMRT or VMAT were retrospectively identified. Both a double-arc VMAT and a 7-field IMRT plan were generated for each of the 10 patients using the same defined tumor volumes, organs at risk (OAR) volumes, dose, fractionation, and optimization constraints. The planning tumor volume (PTV) maximum dose (55.8 Gy vs. 54.4 Gy), PTV mean dose (53.9 Gy vs. 52.1 Gy), and conformality index (1.11 vs. 0.99) were statistically similar between the IMRT and VMAT plans, respectively. The VMAT plans had a statistically significant reduction in monitor units compared with the IMRT plans (1109 vs. 498, p < 0.001). In addition, the doses to the liver, small bowel, and spinal cord were comparable between the IMRT and VMAT plans. However, the VMAT plans demonstrated a statistically significant reduction in the mean left kidney V₂₅ (9.4 Gy vs. 2.3 Gy, p = 0.018), mean right kidney V₁₅ (53.4 Gy vs. 45.9 Gy, p = 0.035), V₂₀ (32.2 Gy vs. 25.5 Gy, p = 0.016), and V₂₅ (21.7 Gy vs. 14.9 Gy, p = 0.001). VMAT was investigated in patients with pancreatic malignancies and compared with the current standard of IMRT. VMAT was found to have similar or improved dosimetric parameters for all endpoints considered. Specifically, VMAT provided reduced monitor units and improved bilateral kidney normal tissue dose. The clinical relevance of these benefits in the context of pancreatic cancer patients, however, is currently unclear and requires further investigation.     

胸上段食管癌螺旋断层放疗和容积旋转调强放疗的剂量学比较

目的 比较胸上段食管癌螺旋断层(HT)与容积旋转调强放疗(VMAT)计划的剂量学差异。方法 随机抽样法选取10例胸上段食管癌患者,分别设计HT和VMAT双弧照射调强放疗计划,肿瘤靶区体积(GTV)给予66 Gy/30次,计划靶区体积(PTV)给予50 Gy/30次。根据剂量体积直方图(DVH)评价靶区的D_1%、D_5%、D_95%、D_99%、适形指数(CI)、均匀性指数(HI)和危及器官(OAR)受量,比较治疗时间和机器跳数(MU)的差异。结果 HT组GTV和PTV的D_99%高于VMAT组(t=4.476、3.756,P<0.05);GTV与PTV的D_1%、D_5%、D_95%、HI和CI差异均无统计学意义(P>0.05)。HT组全肺V₁₀、V₁₅、V₂₀和全肺平均剂量(MLD)均显著低于VMAT组(t=-3.369、-4.824、-4.869、-3.657,P<0.05);全肺V₅、V₃₀和脊髓D_max差异均无统计学意义(P >0.05)。HT组治疗时间和MU数均远大于VMAT组(t=13.970、7.982,P<0.05)。结论 HT与VMAT技术均能满足胸上段食管癌放疗剂量要求。HT技术能显著减小双肺受量,而VMAT技术具备明显的效率优势。     

宫颈癌术后螺旋断层放疗与常规加速器调强放疗的剂量学比较

Objective To compare the dosimetric characteristics of helical tomotherapy(HT)and step-and-shoot intensity modulated radiotherapy(IMRT)for post-operative cervix cancer patients. Methods Ten patients with post-operative cervix cancer were enrolled in this study.HT and IMRT plans were developed for each patient.The dose distributions of the targets,organs at risk(OARs),CI and HI were analyzed and compared.The prescribed dose was 60 Gy/25 f for CTV1,50 Gy/25 f for CTV2.The iso-dose line of 50 Gy was used.Results The homogeneity indexes(HI)(0.94±0.03),conformity index(C1)(1.28±0.02)in HT group were better than in IMRT group(0.85±0.01 and 1.36±0.03),respectively(t=5.12,-6.34,P<0.001).The Dmean of PTV in HT group(51.77 Gy)was lower than that in IMRT group(54.53 Gy)(t=-8.01,P<0.05).The Dmax ,Dmean,V30,V40 and V50 of bladder、rectum and small bowel were lower in HT group than those in IM RT group.The Dmax,Dmean,V30 and V40 of right and left femoral head were lower in HT group than those in IMRT group.Conclusion Helical tomotherapy treatment plan has a better homogeneity,steeper dose gradient,and a better protection for organs at risk.     

宫颈癌术后螺旋断层放疗与常规加速器调强放疗的剂量学比较

目的 研究宫颈癌术后螺旋断层放疗(helical tomotherapy,HT)与常规静态调强放疗(IMRT)的剂量学特点。方法 采用10例宫颈癌术后患者CT图像,统一勾画靶区及危及器官(膀胱、直肠、小肠及双侧股骨头),分别传输至HT计划系统和IMRT计划系统,比较两组计划剂量体积直方图、适形度指数(CI)、均匀指数(HI)和危及器官所接受的照射剂量和体积,统一给予阴道残端60 Gy/25次,亚临床病灶50 Gy/25次,同时限定膀胱、直肠、小肠、股骨头等危及器官受照射剂量与体积。统一应用50 Gy处方剂量评价和比较CI和HI。结果 HT组适形指数(0.94±0.03)和均匀指数(1.28±0.02)均明显好于IMRT组(0.85±0.01和1.36±0.03)(t =5.12和-6.34, P<0.01);HT组PTV平均剂量为51.77Gy显著低于IMRT组54.53Gy(t =-8.01, P<0.05);HT组膀胱、直肠和小肠最大剂量、平均剂量、V₃₀、V₄₀和V₅₀照射体积均显著低于IMRT组;HT组左、右侧股骨头最大剂量、平均剂量、V₃₀和V₄₀照射体积均显著低于IMRT组。结论 HT与IMRT计划均有较好的靶区剂量分布,但HT组在适形指数、均匀指数及对周围危及器官的保护均比IMRT组有明显优势。     

宫颈癌术后螺旋断层放疗与常规加速器调强放疗的剂量学比较

Objective To compare the dosimetric characteristics of helical tomotherapy(HT)and step-and-shoot intensity modulated radiotherapy(IMRT)for post-operative cervix cancer patients. Methods Ten patients with post-operative cervix cancer were enrolled in this study.HT and IMRT plans were developed for each patient.The dose distributions of the targets,organs at risk(OARs),CI and HI were analyzed and compared.The prescribed dose was 60 Gy/25 f for CTV1,50 Gy/25 f for CTV2.The iso-dose line of 50 Gy was used.Results The homogeneity indexes(HI)(0.94±0.03),conformity index(C1)(1.28±0.02)in HT group were better than in IMRT group(0.85±0.01 and 1.36±0.03),respectively(t=5.12,-6.34,P<0.001).The Dmean of PTV in HT group(51.77 Gy)was lower than that in IMRT group(54.53 Gy)(t=-8.01,P<0.05).The Dmax ,Dmean,V30,V40 and V50 of bladder、rectum and small bowel were lower in HT group than those in IM RT group.The Dmax,Dmean,V30 and V40 of right and left femoral head were lower in HT group than those in IMRT group.Conclusion Helical tomotherapy treatment plan has a better homogeneity,steeper dose gradient,and a better protection for organs at risk.     

快速旋转调强与固定射野动态调强在直肠癌术前放疗中的剂量学比较

目的 比较快速旋转调强(RapidArc)与固定射野动态调强(dIMRT)两种放射治疗技术在直肠癌术前放疗中的剂量学差异.方法 采用两种治疗技术对10例Ⅱ、Ⅲ期直肠癌术前患者设计同步加量治疗计划.处方剂量为GTV 50.6 Gy,分22次;PTV41.8 Gy,分22次,危及器官限量参考临床常规要求.在95%体积的PTV达到处方剂量前提下,比较两种计划的剂量体积直方(DVH)图、靶区和危及器官剂量、靶区剂量适形度、剂量分布均匀性、机器跳数以及治疗时间.结果 RapidArc计划中,GTV和PTV的靶区剂量适形度较高(t=7.643、8.226,P＜0.05);而靶区剂量均匀性略低于dIMRT(t=-10.065、-4.235,P＜0.05).RapidArc计划中大、小肠的平均受量显著低于dIMRT计划(t=2.781,P＜0.05).膀胱平均受照剂量略低于dIMRT,股骨头的平均受量略高于dIMRT,但差异无统计学意义.RapidArc计划机器跳数减少48.5%,平均治疗时间节省79.5%.结论 RapidArc与dIMRT计划在直肠癌术前放射治疗的剂量学上无明显差异.RapidArc每次治疗时间明显缩短,减少了治疗期间患者非主观运动引起的误差,总的机器跳数降低,减少了正常组织照射.

Abstract：

Objective To compare the dosimetric difference between RapidArc and fixed gantry angle dynamic intensity modulated radiotherapy (dIMRT) in developing the pre-operative radiotherapy for rectal cancer patients.Methods Two techniques,RapidArc and dIMRT,were used respectively to develop the synchronous intensity modulated plans for 10 stage Ⅱ and Ⅲ rectal cancer patients at the dose of gross tumor volume (GTV) of 50.6 Gy divided into 22 fractions and planning target volume (PTV) of 41.8 Gy divided into 22 fractions.Both plans satisfied the condition of 95% of PTV covered by 41.8 Gy.The dose-volume histogram data,isodose distribution,monitor units,and treatment time were compared.Results The two kinds of dose volume histogram (DVH) developed by these two techniques were almost the same.The conformal indexes of GTV and PTV by RapidArc were better than those by dIMRT (t =7.643,8.226 ,P < 0.05),while the homogeneity of target volume by dIMRT was better (t =-10.065,-4.235 ,P <0.05).The dose of rectum and small bowel planned by RapidArc was significantly lower than that by dIMRT (t =2.781 ,P <0.05).There were no significant differences in the mean doses of bladder and femoral head between these two techniques.The mean monitor units of RapidArc was 475.5,fewer by 48.5% in comparison with that by the dIMRT (924.6).The treatment mean time by RapidArc was 1.2min,shorter by 79.5% in comparison with that by dIMRT (5.58 min).Conclusions There is no significant dosimetric difference between the two plans of RapidArc and dIMRT.Compared with dIMRT,RapidArc achieves equal target coverage and organs at risk(OAR) sparing while using fewer monitor units and less time during radiotherapy for patient with rectal cancer.     

VMAT与IMRT在局部晚期宫颈癌放疗中的剂量学差异

目的 比较分析容积弧形调强放射治疗（VMAT）与固定野调强适形放射治疗（IMRT） 在局部晚期宫颈癌延伸野放疗计划中的剂量学差异。 方法 回顾性分析2019年1月至2021年12月南京医科大学附属淮安第一医院收治的20例宫颈癌患者的临床资料,患者年龄（56.3±9.1）岁,范围39~78岁,均行CT扫描,对所有患者进行计划靶区（PTV）、转移淋巴结计划靶区（PGTVnd）以及膀胱、直肠、双侧股骨头、 肝、双肾、小肠、脊髓等危及器官的勾画。按照随机数字表法将患者分为IMRT 组和VMAT组,每组10例,分别进行IMRT 和VMAT的放疗计划;其中IMRT 组患者年龄（54.1±7.1）岁,VMAT组患者年龄（58.1±10.8）岁。比较2组患者靶区的剂量参数、危及器官的剂量参数以及机器总跳数、有效治疗时间。计量资料的组间比较采用t检验。 结果 在PTV中,VMAT组的适形指数（0.81±0.03）高于IMRT组（0.79±0.23）,且差异有统计学意义（t=−2.190,P=0.035）。在PGTVnd中,VMAT组的均匀性指数（0.06±0.01）低于IMRT组（0.07±0.01）,且差异有统计学意义（t=−2.315,P=0.026）。在膀胱受照射剂量中,VMAT组的V20 Gy（Vx Gy表示接受≥x Gy照射的体积占总体积的百分比）为（92.64±2.29）%,低于IMRT组的（93.98±1.47）%,且差异有统计学意义（t=2.220,P=0.032）。在直肠受照射剂量中,VMAT组的V20 Gy为（92.20±2.21）%,低于IMRT组的（93.68±1.88）%,且差异有统计学意义（t=2.282,P=0.028）。在肝受照射剂量中,VMAT组的V10 Gy、V20 Gy分别为（7.73±0.39）%、（5.14±0.68）%,均低于IMRT组的V10 Gy[（7.93±0.10）%]、V20 Gy[（5.51±0.16）%],且差异均有统计学意义（t=2.372、2.367,P=0.023、0.023）。在小肠受照射剂量中,VMAT组的V20 Gy、V30 Gy、V40 Gy和平均剂量（Dmean）分别为（77.67±4.64）%、（39.21±1.10）%、（18.35±3.05）%和（30.36±3.46） Gy,均低于IMRT组的V20 Gy[（80.24±1.05）%]、V30 Gy[（42.34±6.00）%]、V40 Gy[（22.34±6.01）%]和Dmean[（34.23±6.71） Gy],且差异均有统计学意义（t=2.228~2.628,均P<0.05）。在脊髓受照射剂量中,VMAT组的V20 Gy和Dmean分别为（38.81±2.33）%和（11.46±4.26） Gy,均低于IMRT组的V20 Gy[（42.88±6.19）%]和Dmean[（17.97±7.40） Gy],且差异均有统计学意义（t=2.752、3.410,P=0.009、0.002）。在左肾受照射剂量中,VMAT组的V20 Gy和Dmean分别为（11.67±2.36）%和（10.02±2.19） Gy,均低于IMRT组的V20 Gy[（15.56±7.50）%]和Dmean[（14.06±7.29） Gy],且差异均有统计学意义（t=2.216、2.375,P=0.033、0.023）。在右肾受照射剂量中,VMAT组的V20 Gy和Dmean分别为（11.72±2.31）%和（10.07±2.15） Gy,均低于IMRT组的V20 Gy[（16.67±6.92）%]和Dmean[（13.92±7.17） Gy],且差异均有统计学意义（t=3.030、2.295,P=0.004、0.027）。在左股骨头受照射剂量中,VMAT组的 V10 Gy、V20 Gy、V30 Gy、V40 Gy、V50 Gy及Dmean均低于IMRT组[（74.77±2.33）%对（78.51±7.46）%、（34.37±2.74）%对（38.91±7.20）%、（14.77±2.33）%对（18.51±7.46）%、（2.99±1.03）%对（4.98±3.73）%、（0.48±0.22）%对（0.99±0.65）%、（34.32±2.79） Gy对（38.41±6.67） Gy],且差异均有统计学意义（t=2.147~3.359,均P<0.05）。在右股骨头受照射剂量中,VMAT组的 V50 Gy为（0.02±0.01）%,低于 IMRT组的V50 Gy[0.03±0.01%],且差异有统计学意义（t=2.997,P=0.005）。VMAT组的机器总跳数为（536.16±42.37）,低于IMRT组的（614.44±59.44）,且差异有统计学意义（t=−5.362,P<0.001）;VMAT组的有效治疗时间为（152.23±0.31） min,短于IMRT组的（453.88±9.94） min,且差异有统计学意义（t=−151.708,P<0.001）。 结论 对于局部晚期宫颈癌,VMAT计划的适形度及均匀性较好,更能保护危及器官,且可减少机器跳数,缩短治疗时间。     

Image-guided volumetric modulated arc therapy for breast cancer: a feasibility study and plan comparison with three-dimensional conformal and intensity-modulated radiotherapy

Objective:

To test the feasibility of volumetric modulated arc therapy (VMAT) in breast cancer and to compare it with three-dimensional conformal radiotherapy (3D-CRT) as conventional tangential field radiotheraphy (_conTFRT).

Methods:

12 patients (Stage I, 8: 6 left breast cancer and 2 right breast cancer; Stage II, 4: 2 on each side). Three plans were calculated for each case after breast-conserving surgery. Breast was treated with 50 Gy in four patients with supraclavicular lymph node inclusion, and in eight patients without the node inclusion. Multiple indices and dose parameters were measured.

Results:

V95% was not achieved by any modality. Heterogeneity index: 0.16 (VMAT), 0.13 [intensity-modulated radiotherapy (IMRT)] and 0.14 (_conTFRT). Conformity index: 1.06 (VMAT), 1.15 (IMRT) and 1.69 (_conTFRT). For both indices, IMRT was more effective than VMAT (p=0.009, p=0.002). D_mean and V20 for ipsilateral lung were lower for IMRT than VMAT (p=0.0001, p=0.003). D_mean, V2 and V5 of contralateral lung were lower for IMRT than VMAT (p>0.0001, p=0.005). Mean dose and V5 to the heart were lower for IMRT than for VMAT (p=0.015, p=0.002).

Conclusion:

The hypothesis of equivalence of VMAT to IMRT was not confirmed for planning target volume parameter or dose distribution to organs at risk. VMAT was inferior to IMRT and 3D-CRT with regard to dose distribution to organs at risk, especially at the low dose level.

Advances in knowledge:

New technology VMAT is not superior to IMRT or conventional radiotherapy in breast cancer in any aspect.In Western countries, one in every eight females is diagnosed with breast cancer. Breast-conserving surgery with post-operative radiotherapy (RT) is the primary therapeutic strategy for Stages I and II of breast cancer. Systemic therapy is also part of the primary therapeutic strategy in most patients with Stage I and II breast cancer. RT substantially reduces the rate of local relapse and improves long-term survival [1]. However, RT is suggested to be associated with morbidity of the heart [2,3], lung [4,5], subcutaneous tissue and skin [6] and a risk of secondary malignancies [7–9].A large body of available data regarding the potential toxicity of RT was published between 1980 and the end of 1990 [1]. Special clinical interest has been focused on acute and mostly transient lung and skin toxicity, axillary problems and late cardiac events, in addition to the risk of secondary malignancies. This period was characterised by RT delivery using a fluoroscopic technique with two-dimensional planning followed by three-dimensional (3D) conformal techniques with two conventional tangential field radiotherapy (_conTFRT) fields. _conTFRT encompassed the whole breast, skin, minor ipsilateral lung volume, a part of the axillary region at Level 1 and a part of the heart in the case of left-sided cancer [10–12]. These areas have been sites for local toxicity, because RT principles, and thus homogeneous photon flux across treatment fields, remained unchanged.Intensity-modulated radiotherapy (IMRT) has been implemented in the past decade, permitting variation of fluence modulation across fields and allowing optimal dose administration according to an individual''s anatomy. IMRT results in improved avoidance of critical structures such as the heart, skin, axillary region and lung, while facilitating necessary tumour volume coverage [13,14]. Clinical data on IMRT show an improvement in dose homogeneity within the irradiated breast and sparing of the heart and lung [14–17]. However, a disadvantage of IMRT over _conTFRT is the long treatment duration owing to the higher number of fields and monitor units (MUs) involved. In addition, although IMRT reduces the volume of the heart and ipsilateral lung that receive high doses, it is associated with an increase in overall low-dose radiation. Despite the available clinical data, the wider use and specific indications for IMRT for breast cancer have not been established.In volumetric modulated arc therapy (VMAT), technical extension of conventional fixed-field IMRT, an optimised dose distribution is possible with a single gantry rotation. Studies have shown that VMAT reduces the number of MUs and treatment delivery time [18–22], with similar or better planning target volume (PTV) coverage and sparing of organs at risk (OARs) than IMRT. Reports on VMAT for breast cancer are few and mainly concern planning comparisons [20,23–28] and very preliminary clinical data [29].The RapidArc® system (Varian Medical Systems, Palo Alto, CA) has recently been introduced in our department. Accordingly, we have begun examining the potential of RapidArc VMAT for breast cancer treatment in a prospective clinical setting to adequately evaluate dosimetric parameters, treatment planning and clinical implications as well the disadvantages.The present study aimed to compare the use of RapidArc VMAT with IMRT and _conTFRT for breast cancer therapy. We hypothesised that the use of RapidArc under routine clinical circumstances would be equivalent to or better than IMRT and _conTFRT in terms of PTV coverage and OAR sparing, while reducing both treatment time and MUs.     

High-dose radiotherapy in inoperable nonsmall cell lung cancer: Comparison of volumetric modulated arc therapy,dynamic IMRT and 3D conformal radiotherapy

Conformal 3D radiotherapy (3D-CRT) combined with chemotherapy for inoperable non–small cell lung cancer (NSCLC) to the preferable high dose is often not achievable because of dose-limiting organs. This reduces the probability of regional tumor control. Therefore, the surplus value of using intensity-modulated radiation therapy (IMRT) techniques, specifically volumetric modulated arc therapy (RapidArc [RA]) and dynamic IMRT (d-IMRT) has been investigated. RA and d-IMRT plans were compared with 3D-CRT treatment plans for 20 patients eligible for concurrent high-dose chemoradiotherapy, in whom a dose of 60 Gy was not achievable. Comparison of dose delivery in the target volume and organs at risk was carried out by evaluating 3D dose distributions and dose-volume histograms. Quality of the dose distribution was assessed using the inhomogeneity and conformity index. For most patients, a higher dose to the target volume can be delivered using RA or d-IMRT; in 15% of the patients a dose ≥60 Gy was possible. Both IMRT techniques result in a better conformity of the dose (p < 0.001). There are no significant differences in homogeneity of dose in the target volume. IMRT techniques for NSCLC patients allow higher dose to the target volume, thus improving regional tumor control.     

Dosimetric and radiobiological comparison of helical tomotherapy, forward-planned intensity-modulated radiotherapy and two-phase conformal plans for radical radiotherapy treatment of head and neck squamous cell carcinomas

Objectives

The usual radical radiotherapy treatment prescribed for head and neck squamous cell carcinoma (HNSCC) is 70 Gy (in 2 Gy per fraction equivalent) administered to the high-risk target volume (TV). This can be planned using either a forward-planned photon-electron junction technique (2P) or a single-phase (1P) forward-planned technique developed in-house. Alternatively, intensity-modulated radiotherapy (IMRT) techniques, including helical tomotherapy (HT), allow image-guided inversely planned treatments. This study was designed to compare these three planning techniques with regards to TV coverage and the dose received by organs at risk.

Methods

We compared the dose–volume histograms and conformity indices (CI) of the three planning processes in five patients with HNSCC. The tumour control probability (TCP), normal tissue complication probability (NTCP) and uncomplicated tumour control probability (UCP) were calculated for each of the 15 plans. In addition, we explored the radiobiological rationality of a dose-escalation strategy.

Results

The CI for the high-risk clinical TV (CTV1) in the 5 patients were 0.78, 0.76, 0.82, 0.72 and 0.81 when HT was used; 0.58, 0.56, 0.47, 0.35 and 0.60 for the single-phase forward-planned technique and 0.46, 0.36, 0.29, 0.22 and 0.49 for the two-phase technique. The TCP for CTV1 with HT were 79.2%, 85.2%, 81.1%, 83.0% and 53.0%; for single-phase forward-planned technique, 76.5%, 86.9%, 73.4%, 81.8% and 31.8% and for the two-phase technique, 38.2%, 86.2%, 42.7%, 0.0% and 3.4%. Dose escalation using HT confirmed the radiobiological advantage in terms of TCP.

Conclusion

TCP for the single-phase plans was comparable to that of HT plans, whereas that for the two-phase technique was lower. Centres that cannot provide IMRT for the radical treatment of all patients could implement the single-phase technique as standard to attain comparable TCP. However, IMRT produced better UCP, thereby enabling the exploration of dose escalation.     

旋转调强与固定野逆向调强放疗在颅脑多发转移瘤中的剂量学比较研究

目的 比较旋转调强(RapidArc)与固定野调强(IMRT)放疗在颅脑多发转移瘤中的剂量学差异。方法 针对10例多发脑转移瘤患者分别设计3种放疗计划:固定野逆向调强(IMRT),RapidArc单弧旋转调强(RA1),双弧旋转调强(RA2)。在保证计划均满足临床要求前提下,分别比较3种计划的靶区剂量分布、危及器官及靶区外正常组织的受照剂量、机器跳数以及治疗时间,探讨其剂量学差异。结果 3种计划均满足临床要求,在靶区适形度和均匀性方面,RA2计划优于IMRT(Z＝-2.803、-2.094,P<0.05)和RA1(Z＝-2.448、-2.191,P＜0.05),RA1计划与IMRT计划差别不大。RA1、RA2计划中的双侧晶体、双侧眼球、脑干的最大剂量均显著低于IMRT(Z＝-2.803～-2.191,P <0.05)。RA2计划评估的双侧视神经最大剂量均显著低于IMRT(Z＝-2.293、-2.701,P<0.05)。RA1、RA2计划中的机器跳数相对于IMRT平均分别减少了43%和24%,缩短了治疗时间。结论 单弧和双弧旋转调强计划均可达到或优于IMRT计划的靶区剂量分布,能更好地降低部分危及器官的受照剂量,同时可以显著降低机器跳数和治疗实施时间。     

旋转调强与固定野逆向调强放疗在颅脑多发转移瘤中的剂量学比较研究

Objective To evaluate the performace of fixed field Intensity modulated radiation therapy (IMRT) and RapidArc in the radiotherapy for multiple intracranial metastases.Methods The clinical data of 10 patients with multiple intracranial metastases,8 male and 2 female,aged 65-73,were used to design 3 plans:fixed field IMRT,RapidArc with single Arc (RA1),and RapidArc with double Arc (Arc 2).Dose-volume-histogram analysis was used to compare dose results,monitor unit,and delivery time.Results All 3 plans met the clinical requirements.The best target conformity and homogeneity were observed in the RA2 plan (Z = -2.803,- 2.904,P ＜ 0.05) and there were no statistical differences between the IMRT plan and RA1 plan.The maximum doses to the lens,eyes,and brainstem of the two RapidArc plans were all significantly lower than those of the IMRT plan(Z = -2.803--2.191 ,P ＜0.05),and the maximum dose to the optic nerves of the RA2 plan was significantly lower than that of the IMRT plan (Z = -2.293,-2.701 ,P ＜0.05).Compared with the IMRT plan,the average monitor units of the RA1 and RA2 plans were reduced by 29% and 24%,respectively,and the delivery time of these plans were significantly shorter by 84% and 69%,respectively.Conclusions Compared to the IMRT plan,RapidArc plans with single or double Arcs show similar or better effects in the target dose distribution,reduction of irradiation doses on organs at risk and,moreover,significant decrease of the monitor units and delivery time.