Dose comparisons for conformal, IMRT and VMAT prostate plans

Purpose: Volumetric‐modulated arc therapy (VMAT) is a relatively new treatment technique in radiation therapy. A comparison study of conformal, intensity‐modulated radiation therapy (IMRT) and single‐ and double‐arc VMAT plans was undertaken to evaluate the dosimetric impact of this new technology in prostate cases. The research questions were as follows: how does VMAT dosimetry compare with IMRT and conformal plans?; does VMAT increase the volume of bowel receiving lower doses?; are one or two VMAT arcs required for standard prostate cases? Methods: Eight prostate cancer and post‐prostatectomy patients were randomly selected for this study. Conformal, IMRT and single and double Arc VMAT plans were generated and dosimetric evaluations were performed. Each plan was prescribed a total of 75.6 Gy over a course of 42 fractions to the planning target volume (PTV). Results: The Healthy Tissue Conformity Index and the conformation number results revealed the IMRT and two VMAT techniques to have superior dosimetry to the PTV compared with the conformal plans. The maximum dose delivered to the PTV was significantly higher with the single‐arc VMAT technique compared with the conformal or double‐arc VMAT plans. There were no significant differences between the planning techniques for the bladder and small bowel dosimetry. However, IMRT and VMAT plans delivered less radiation to the rectum and femoral heads, and a single‐arc VMAT plan was optimal for the right femoral head and the two VMAT techniques were optimal to the IMRT plans for the left femoral head. Conclusions: Single‐ and double‐arc VMAT consistently resulted in favourable or slightly superior dosimetry when compared with static gantry IMRT for prostate cases. Both the VMAT techniques and static gantry IMRT resulted in superior critical tissue sparing when compared with conformal plans.     

IMRT、VMAT及HT技术在肺癌SBRT应用中的比较

肺癌立体定向放疗的主要技术包括调强放疗(IMRT)、容积旋转调强放疗(VMAT)和螺旋断层放疗(HT).3种技术在靶区适形度及剂量均匀性方面,HT和VMAT要优于IMRT,但HT和VMAT技术会增加肺的低剂量区受照体积.VMAT较其他两种技术可明显缩短治疗时间.目前,对于不同位置、不同分期的肺部肿瘤,如何个体化地选择最佳放疗技术仍存有一定的争议.     

早期乳腺癌保乳术后4种放疗技术的剂量参数比较

目的：比较早期乳腺癌保乳术后常规切线野（TW）、野中野调强（FIF - IMRT）、切线逆向调强（T -IMRT）和容积调强（VMAT）4种放射治疗技术的靶区和危及器官的剂量参数。方法：15例左侧早期（pT1-2 N0 M0）乳腺癌患者保乳术后接受放疗。CT 模拟定位扫描后勾画靶区和危及器官,在同一患者 CT 影像上分别做 TW、FIF - IMRT、T - IMRT 和 VMAT 4种治疗计划设计。PTV 剂量为50Gy,V47.5≥95%。4种计划的剂量限制相同。在剂量-体积直方图中读取4种计划靶区剂量的分布参数,心脏、双侧肺脏及对侧乳腺受照剂量和体积,对各参数的均数进行比较,并比较4组平均机器跳数差异。结果：4种计划都满足 V47.5≥95%。VMAT 与 T - IMRT、FIF - IMRT 和 TW 计划相比,明显提高了靶区适行指数（CI,P ﹤0.05）。VMAT、T - IMRT和 FIF - IMRT 与 TW 相比,明显改善了靶区均匀性指数（HI,P ﹤0.05）。VMAT 增加了危及器官（心脏和同侧肺脏）V 5、V10和 V20的受照射体积,但是没有增加﹥ V30的照射体积。VMAT 明显增加了右侧乳腺和右侧肺脏照射剂量（P ﹤0.05）,T - IMRT 和 FIF - IMRT 明显降低了右侧乳腺和右侧肺脏照射剂量（P ﹤0.05）。VMAT 与T - IMRT、FIF - IMRT 和 TW 相比,明显增加了机器跳数（P ﹤0.05）。结论：早期乳腺癌保乳术后放射治疗4种计划比较,VMAT 明显提高了靶区的适行性和均匀性,增加了正常组织的受照射剂量和机器跳数,延长了治疗时间。T - IMRT 和 FIF - IMRT 也提高了靶区的适行性和均匀性,降低了正常组织的受照射剂量。     

A Dosimetric and Radiobiological Comparison of Intensity Modulated Radiotherapy,Volumetric Modulated Arc Therapy and Helical Tomotherapy Planning Techniques in Synchronous Bilateral Breast Cancer

Objective: The present investigation intends to identify the optimal radiotherapy treatment plan for synchronous bilateral breast cancer (SBBC) using dosimetric and radiobiological indexes for three techniques, namely, helical tomotherapy (HT), volumetric modulated arc therapy (VMAT), and intensity-modulated radiotherapy (IMRT). Methods: Twenty SBBC treated female patients treatment planning data (average age of 52.5 years) were used as the sample for the present study. Three different plans were created using 50 Gy in a 25 fraction dose regime. Poisson, Niemierko, and LKB models were applied for calculating normal tissue complication probability (NTCP) and tumour control probability (TCP). Result: The target average dose comparison between IMRT with HT and VMAT with HT was highly substantial (P=0.001). The percentage of TCP for IMRT, VMAT, and HT in the Poisson model were 93.70±0.28, 94.68±0.30, and 94.34±0.57, respectively (p<0.05). The dose maximum was lower for the whole lung in the HT plan, with an average dose of 49.31Gy±3.9 (p<0.009). The NTCP values of both Niemierko and LKB models were lower for the heart, lungs, and liver for the IMRT plan. Conclusion: The sparing of organs at risk was higher in the HT plan dosimetrically, and the TCP was higher in the three techniques. The comparison between the three techniques shows that the IMRT and HT techniques could be considered for treating SBBC.     

左侧乳腺癌保乳术后3种放疗技术在同步推量中的剂量学研究

目的 探讨左侧乳腺癌保乳术后半弧容积动态旋转调强(VMAT)放疗、切线弧VMAT放疗和逆向调强放疗(IMRT)3种放疗技术在同步推量中的剂量学差异.方法 选取10例左侧乳腺癌保乳术后患者,使用MONACO 5.1计划系统,分别采用半弧VMAT、切线弧VMAT和IMRT三种放疗技术,处方剂量均为计划靶区(PTV)50 Gy/25 f、计划肿瘤靶区(PGTV)60 Gy/25 f,评估3种计划靶区剂量适形度指数(CI)、均匀性指数(HI)以及周围正常组织器官的受照剂量.结果 半弧VMAT的PGTV靶区CI优于IMRT(P﹤0.05).切线弧VMAT放疗技术较IMRT放疗技术降低了左侧乳腺癌保乳术后患者患侧肺组织V10的照射范围(P=0.04).切线弧VMAT放疗技术较半弧VMAT放疗技术降低了左侧乳腺癌保乳术后患者健侧肺组织V5(P﹤0.001)、V10(P=0.04)、心脏的V10(P=0.01)、Dmean(P=0.01)及健侧乳腺组织V5(P﹤0.01)的剂量范围.而IMRT放疗技术降低了左侧乳腺癌保乳术后患者健侧肺组织V5、V10的剂量范围(P﹤0.05).结论 对于左侧乳腺癌保乳术后患者的同步推量放疗,VMAT放疗技术尤其是半弧VMAT放疗技术具有更好的靶区适形性;切线弧VMAT放疗技术可以降低周围大部分正常组织器官的照射剂量.     

A treatment planning study comparing whole breast radiation therapy against conformal, IMRT and tomotherapy for accelerated partial breast irradiation.

PURPOSE AND BACKGROUND: Conventional early breast cancer treatment consists of a lumpectomy followed by whole breast radiation therapy. Accelerated partial breast irradiation (APBI) is an investigational approach to post-lumpectomy radiation for early breast cancer. The purpose of this study is to compare four external beam APBI techniques, including tomotherapy, with conventional whole breast irradiation for their radiation conformity index, dose homogeneity index, and dose to organs at risk. METHODS AND MATERIALS: Small-field tangents, three-dimensional conformal radiation therapy, intensity-modulated radiation therapy and helical tomotherapy were compared for each of 15 patients (7 right, 8 left). One radiation conformity and two dose homogeneity indices were used to evaluate the dose to the target. The mean dose to organs at risk was also evaluated. RESULTS: All proposed APBI techniques improved the conformity index significantly over whole breast tangents while maintaining dose homogeneity and without a significant increase in dose to organs at risk. CONCLUSION: The four-field IMRT plan produced the best dosimetric results; however this technique would require appropriate respiratory motion management. An alternative would be to use a four-field conformal technique that is less sensitive to the effects of respiratory motion.     

Quelle RCMI ? Du « step and shoot » au VMAT : point de vue du physicien

Intensity-modulated radiation therapy (IMRT) is essential to have a dose distribution matching with the planning target volume (PTV) in case of concave-shape target. Today IMRT delivery techniques with linear accelerator can be divided into two classes: techniques with fixed gantry, called “step and shoot” (S&S) and “sliding window” (SW), and rotational techniques, called intensity modulated arc therapy (IMAT) and volumetric modulated arc therapy (VMAT). We discuss about constraints for IMRT implementation from dosimetric planning to treatment delivery. We compare S&S and VMAT performances concerning dose distribution quality, efficiency and delivery time. We describe quality controls that must be implemented and the methods for analysis and follow-up performances. VMAT tends to yield similar dose distribution to MRT with fixed gantry. VMAT also decreases monitor units as well as treatment delivery time to less than 5 minutes. However, VMAT is an IMRT technique more difficult to master than S&S technique because there are more variable parameters.     

Cost‐effectiveness analysis of intensity‐modulated radiation therapy with normal and hypofractionated schemes for the treatment of localised prostate cancer

The aim of our analysis was to compare the cost‐effectiveness of high‐dose intensity‐modulated radiation therapy (IMRT) and hypofractionated intensity‐modulated radiation therapy (HF‐IMRT) versus conventional dose three‐dimensional radiation therapy (3DCRT) for the treatment of localised prostate cancer. A Markov model was constructed to calculate the incremental quality‐adjusted life years and costs. Transition probabilities, adverse events and utilities were derived from relevant systematic reviews. Microcosting in a large university hospital was applied to calculate cost vectors. The expected mean lifetime cost of patients undergoing 3DCRT, IMRT and HF‐IMRT were 7,160 euros, 6,831 euros and 6,019 euros respectively. The expected quality‐adjusted life years (QALYs) were 5.753 for 3DCRT, 5.956 for IMRT and 5.957 for HF‐IMRT. Compared to 3DCRT, both IMRT and HF‐IMRT resulted in more health gains at a lower cost. It can be concluded that high‐dose IMRT is not only cost‐effective compared to the conventional dose 3DCRT but, when used with a hypofractionation scheme, it has great cost‐saving potential for the public payer and may improve access to radiation therapy for patients.     

Comparison of Three Dimensional Conformal Radiation Therapy,Intensity Modulated Radiation Therapy and Volumetric Modulated Arc Therapy for Low Radiation Exposure of Normal Tissue in Patients with Prostate Cancer

Radiotherapy has an important role in the treatment of prostate cancer. Three-dimensional conformalradiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT) and volumetric modulated arctherapy (VMAT) techniques are all applied for this purpose. However, the risk of secondary radiation-inducedbladder cancer is significantly elevated in irradiated patients compared surgery-only or watchful waiting groups.There are also reports of risk of secondary cancer with low doses to normal tissues. This study was designed tocompare received volumes of low doses among 3D-CRT, IMRT and VMAT techniques for prostate patients. Tenprostate cancer patients were selected retrospectively for this planning study. Treatment plans were generatedusing 3D-CRT, IMRT and VMAT techniques. Conformity index (CI), homogenity index (HI), receiving 5 Gy ofthe volume (V5%), receiving 2 Gy of the volume (V2%), receiving 1 Gy of the volume (V1%) and monitor units(MUs) were compared. This study confirms that VMAT has slightly better CI while thev olume of low doseswas higher. VMAT had lower MUs than IMRT. 3D-CRT had the lowest MU, CI and HI. If target coverage andnormal tissue sparing are comparable between different treatment techniques, the risk of second malignancyshould be a important factor in the selection of treatment.     

三种全乳同步瘤床加量调强放疗计划的比较

背景与目的：目前保乳手术+术后放疗已成为早期乳腺癌标准治疗模式。采用3种不同适形调强放疗技术制定早期乳腺癌保乳术后全乳同步瘤床加量的放疗计划,并对3种放疗计划的肿瘤靶区、危及器官剂量学参数等方面进行比较。方法：随机选取上海交通大学医学院附属第九人民医院黄浦分院放疗科2018年度收治的女性乳腺癌保乳术后患者50例,左、右侧乳腺癌患者各25例。分别采用正向调强、逆向调强、容积调强等3种调强治疗方法制定全乳同步瘤床加量放疗计划。比较3种放疗计划的靶区适形度（conformity index,CI）与均匀度（homogeneity index,HI）;危及器官的剂量学参数,包括同侧肺（V ₅ 、V ₂₀ 、V ₃₀ ）、心脏（D _mean 、左乳癌V ₂₅ 、右乳癌V ₁₅ ）、对侧乳腺（D ₂ 、D _mean ）;单次治疗的总跳数（minute,MU）及出束时间,并进一步分析乳房体积大小对放疗计划的影响。结果：正向调强、逆向调强与容积调强放疗计划的全乳靶区CI分别为0.69±0.09、0.86±0.06和0.79±0.07（两两比较P<0.001）,瘤床靶区CI分别为0.71±0.15、0.79±0.15和0.80±0.12（两两比较P=0.007、P<0.001和P=0.624）,全乳靶区HI分别为0.17±0.03、0.13±0.03和0.18±0.03（两两比较P<0.001）,瘤床靶区HI分别为0.17±0.05、0.07±0.01和0.10±0.02（两两比较P<0.001）。同侧肺V ₅ 为56.08±7.24、46.08±5.48和57.82±6.64（两两比较P<0.001、P=0.079、P<0.001）,V ₂₀ 为27.96±2.57、20.28±2.13和23.44±2.71（两两比较P<0.001、P=0.025、P<0.001）,V ₃₀ 为22.34±2.20、15.40±2.37和16.42±2.82（两两比较P<0.001、P=0.006、P=0.012）。左乳癌心脏D _mean 为775.48±113.23、584.20±223.04和634.24±174.38（两两比较P<0.001、P<0.001、P=0.045）,右乳癌心脏D _mean 为209.32±84.60、125.56±41.65和200.80±49.74（两两比较P<0.001、P=0.524、P<0.001）,左乳癌心脏V ₂₅ 为8.20±1.73、5.02±1.38和6.65±1.56（两两比较P<0.001、P<0.001、P=0.037）,右乳癌心脏V ₁₅ 均为0值不做比较。对侧乳腺的D _mean 为288.05±105.14、108.25±56.47和123.59±73.79（两两比较P<0.001、P<0.001、P=0.023）。单次治疗MU为285.74±17.73、1463.94±227.74和445.50±98.22（两两比较P<0.001）,出束时间为205.12±20.68、343.26±37.59和138.06±13.53（两两比较P<0.001）。50例患者以患侧乳房体积平均值764.89 mL为界分成两组,乳房小体积组3种放疗计划的靶区CI、HI以及单次MU与出束时间优于乳房大体积组,而在正常器官剂量学方面两组间差异无统计学意义。结论：逆向调强与容积调强在靶区剂量学参数及危及器官的保护方面优于正向调强计划。其中逆向调强计划稍优于容积调强,推荐用于耐受较好、有长期生存预期的中、青年患者;而容积调强计划的单次MU更少,出束时间更短,建议老年、乳房体积较大的患者采用。     

螺旋断层放疗在肿瘤治疗中的应用

螺旋断层放疗是CT和直线加速器结合的放疗设备,具有360度照射、兆伏级螺旋CT(MVCT)影像引导、自适应计划等技术,可进行调强放疗、自适应放疗、立体定向外科等多种功能,适应证广泛.     

左侧乳腺癌放疗相关心脏毒性的危险因素分析

 放射治疗是乳腺癌的重要治疗手段,由于左乳与心脏位置毗邻,设计照射野时常不能完全避开心脏。乳腺癌放射治疗增加了患缺血性心脏病、心包炎和瓣膜病的风险。年轻、高体重指数（body mass index, BMI）、肿瘤位于中央象限和胸骨旁区域与心脏受到高剂量辐射有关。放疗心脏毒性与放疗技术有很大关系,对于左乳切除术后放疗,多野调强适形放疗（IMRT）能够平衡靶区覆盖和正常组织受量,而左乳保乳术后放疗,采用双弧度容积旋转调强（VMAT）较多野IMRT更具优势。相比全乳照射,加速部分乳腺照射能够显著降低心脏剂量;而对于需要照射区域淋巴结的患者,采用容积旋转调强或螺旋断层放疗在减少心脏受量方面则显示出优势。相比自由呼吸,深吸气屏气放疗能够显著减少心脏和冠状动脉左前降支剂量;尤其是对于胸壁+区域淋巴结（包括内如淋巴结）放疗的患者采用深吸气屏气（deep inspiration breath hold, DIBH）放疗获益更多,而对于保乳术后仍为大乳腺的患者,采用俯卧位能减少心脏毒性。另外,左乳放疗期间同步曲妥珠单抗靶向治疗、芳香化酶抑制剂（aromatase inhibitors, AI）会影响心脏事件的发生。基于上述因素,在给左侧乳腺癌患者制定放疗计划时,应结合患者年龄、BMI、原发肿瘤位置、体型、术后乳腺大小、是否需要区域淋巴结照射,根据现有放疗设备,给予最优的放疗方案,同时减少增加心脏毒性的同步治疗,从而最大程度减少治疗导致的心脏不良反应。     

Postmastectomy Radiation Therapy Planning After Immediate Implant-based Reconstruction Using the European Society for Radiotherapy and Oncology-Advisory Committee in Radiation Oncology Practice Consensus Guidelines for Target Volume Delineation

AimsTo evaluate how common radiation therapy techniques perform in the setting of the new European Society for Radiotherapy and Oncology-Advisory Committee in Radiation Oncology Practice (ESTRO-ACROP) delineation recommendations for immediate breast reconstruction (IBR).Materials and methodsSeven Danish radiation therapy centres and six international European centres participated in this project. Two breast cancer cases (one left-sided and one right-sided) with a retropectoral implant were chosen for radiation therapy planning using deep-inspiration breath-hold. Target volumes were delineated according to ESTRO-ACROP delineation recommendations. The centres were asked to plan the cases using any radiation therapy technique according to the Danish Breast Cancer Group plan objectives.ResultsIn total, 35 treatment plans were collected. Half of the submitted plans, for both the left-sided and the right-sided case, used the field-in-field (FiF) technique (nine for each), a quarter used volumetric arc radiation therapy (VMAT; five for right-sided, four for left-sided) and the remaining quarter was a mix of inverse intensity-modulated radiation therapy (IMRT), helicoidal therapy and hybrid (combined open fields and VMAT) techniques. Mean clinical target volume doses were in the range 99–102% of the prescribed dose. The median FiF mean heart dose (MHD) for right-sided radiation therapy was 1 Gy (range 0.8–3.7) and 5.2 Gy for left-sided radiation therapy (range 2.2–6.5). For right-sided radiation therapy, the median VMAT MHD was 3.42 Gy, for IMRT was 2.3 Gy and for helicoidal therapy was 5.1 Gy. For left-sided radiation therapy, the median VMAT MHD was 6.3 Gy, for IMRT was 7.8 Gy and for helicoidal therapy was 7.3 Gy.ConclusionsDifferent radiation therapy techniques could be used to plan radiation therapy in the setting of IBR. FiF provided good coverage with acceptable organ at risk doses. The best dose distribution results as a trade-off between the objectives of target volume coverage and high-dose organ at risk inclusion. The radiation therapy technique affects the interplay between these objectives.     

三种照射技术在髓母细胞瘤放射治疗中的剂量学分析

目的 探讨调强放射治疗(Intensity modulated radiation therapy,IMRT)、容积调强弧形放疗(Volumetric modulated arc therapy,VMAT)和螺旋断层放射治疗(Helical tomotherapy,TOMO)在髓母细胞瘤放射治疗中的剂量学差异。方法 选取10例髓母细胞瘤儿童患者,设计出IMRT(等分5野)、VMAT(双弧)、TOMO三组放疗计划。分析三种计划靶区的适形指数(CI)、均匀指数(HI)、1.07倍处方剂量线所包含的靶区体积(V₁₀₇)、靶区内最大剂量点剂量值(D_max)、危及器官(OAR)受量情况、机器跳数和治疗时间。结果 对于全脑全脊髓放疗,TOMO组计划靶区PTV的CI、HI、V₁₀₇、D_max和OAR受量都优于VMAT组和IMRT(5野)组计划(P＜0.05);TOMO组计划机器跳数最多(P＜0.05),且其治疗时间最长(P＜0.05);TOMO组可以一次完成全脑全脊髓照射,避免了VMAT和IMRT(5野)治疗时人为移床误差。结论 在髓母细胞瘤放射治疗中,TOMO组在剂量分布上优于VMAT组和IMRT(5野)组,但其治疗时机器跳数和治疗时间明显增加,它对临床上的影响有待于进一步观察与研究。     

左乳腺癌保乳术后放疗不同外照射技术所致皮肤受照剂量的比较

目的:比较3D-CRT、IMRT、VMAT三种技术在左乳腺癌保乳术后放疗中皮肤受照剂量的差异。方法:选取10例左乳腺癌保乳术后患者,为每位患者设计3D-CRT、IMRT、VMAT三种计划,比较三种计划间靶区适形度、均匀指数等剂量学参数及皮肤等危及器官受照剂量。结果:靶区适形度IMRT(0.64±0.04)及VMAT(0.64±0.09)均优于3D-CRT(0.33±0.03)(F=82.2,P＜0.05);均匀指数IMRT及VMAT分别为（0.12±0.02）和（0.11±0.02）,好于3D-CRT（0.14±0.01）（F=8.1,P＜0.05）。皮肤受照剂量比较中V30、V40、V45、V50、Dmean各项指标IMRT及VMAT均好于3C-CRT(F=9.0~125.6,P＜0.05);对IMRT及VMAT作进一步LSD比较:V30、V50、Dmean差异无统计学意义（P分别等于0.109、0.571、0.258）,而V40及V45 VMAT比IMRT分别降低了5.6%和3.47%（P分别等于0.000及0.027）。结论:左乳腺保乳术后放疗中相比于3D-CRT,IMRT及VMAT两种技术提供了更好的靶区剂量同时,能够有效降低患者的皮肤受照剂量;而VMAT相比于IMRT可进一步降低皮肤V40及V45受量。     

容积旋转调强放疗和固定野适形调强放疗治疗中晚期宫颈癌的临床研究

目的:评估中晚期宫颈癌放疗中分别采用容积旋转调强放疗（volumetric modulated arc therapy,VMAT）和5野适形调强放疗（intensity modulated radiotherapy,IMRT）的近期疗效和不良反应。方法:选取2016年4月至2017年3月陕西省肿瘤医院首程收治112例中晚期子宫颈癌（诊断为Ⅱb-Ⅳa期）患者,随机分为VMAT和IMRT 2组,同步给予铂类增敏化疗及后装治疗,观察2种治疗方法疗效及不良反应的差异。结果:两组患者近期疗效相当,1年总体生存率、无局部复发生存率和无远处转移率两组间差异无统计学意义（P＞0.05）;急性放射性肠炎、急性放射性膀胱炎及骨髓抑制发生率两组间差异无统计学意义（P＞0.05）;远期不良反应（放射性膀胱炎及肠炎）,VMAT明显优于IMRT。结论:两种放疗方法对中晚期宫颈癌近期疗效相同,但从长远意义上讲VMAT能更好的保护危及器官,有效降低放射损伤,是治疗中晚期宫颈癌的重要手段。     

Optimising the dosimetric quality and efficiency of post-prostatectomy radiotherapy: a planning study comparing the performance of volumetric-modulated arc therapy (VMAT) with an optimised seven-field intensity-modulated radiotherapy (IMRT) technique

Purpose: The purpose of this study was to compare and evaluate radiotherapy treatment plans using volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) for post‐prostatectomy radiotherapy. Methods and Materials: The quality of radiotherapy plans for 10 patients planned and treated with a seven‐field IMRT technique for biochemical failure post‐prostatectomy were subsequently compared with 10 prospectively planned single‐arc VMAT plans using the same computed tomography data set and treatment planning software. Plans were analysed using parameters to assess for target volume coverage, dose to organs at risk (OAR), biological outcomes, dose conformity and homogeneity, as well as the total monitor units (MU), planning and treatment efficiency. Results: The mean results for the study population are reported for the purpose of comparison. For IMRT, the median dose to the planning target volume, V_95% and D_95% was 71.1 Gy, 98.9% and 68.3 Gy compared with 71.2 Gy, 99.2% and 68.6 Gy for VMAT. There was no significant difference in the conformity index or homogeneity index. The VMAT plans achieved better sparing of the rectum and the left and right femora with a reduction in the median dose by 7.9, 6.3 and 3.6 Gy, respectively. The total number of monitor units (MU) was reduced by 24% and treatment delivery time by an estimated 3 min per fraction without a significant increase in planning requirements. Conclusions: VMAT can achieve post‐prostatectomy radiotherapy plans of comparable quality to IMRT with the potential to reduce dose to OAR and improve the efficiency of treatment delivery.     

Assessment of voluntary deep inspiration breath‐hold with CINE imaging for breast radiotherapy

Deep Inspiration Breath‐Hold (DIBH) techniques for breast cancer radiation therapy (RT) have reduced cardiac dose compared to Free Breathing (FB). Recently, a voluntary deep inspiration breath‐hold (vDIBH) technique was established using in‐room lasers and skin tattoos to monitor breath‐hold. An in‐house quality assessment of positional reproducibility during RT delivery with vDIBH in patients with left‐sided breast cancer was evaluated. The electronic portal imaging device (EPID) was used in cinematographic (CINE) mode to capture a sequence of images during beam delivery. Weekly CINE images were retrospectively assessed for 20 left‐sided breast cancer patients receiving RT in vDIBH, and compared with CINE images of 20 patients treated in FB. The intra‐beam motion was assessed and the distance from the beam central axis (CA) to the internal chest wall (ICW) was measured on each CINE image. These were then compared to the planned distance on digitally reconstructed radiograph (DRR). The maximum intra‐beam motion for any one patient measurement was 0.30 cm for vDIBH and 0.20 cm for FB. The mean difference between the distance from the CA to ICW on DRR and the equivalent distance on CINE imaging (as treated) was 0.28 cm (SD 0.17) for vDIBH patients and 0.25 cm (SD 0.14) for FB patients (P = 0.458). The measured values were comparable for patients undergoing RT in vDIBH, and for those in FB. This quality assessment showed that using in‐room lasers and skin tattoos to independently monitor breath‐hold in vDIBH as detected by ‘on‐treatment’ CINE imaging is safe and effective.     

Reduced acute toxicity associated with the use of volumetric modulated arc therapy for the treatment of adenocarcinoma of the prostate

PurposeNovel techniques to deliver intensity modulated radiation therapy (IMRT) have resulted in improved treatment efficiency and dosimetric endpoints. We aimed to compare acute gastrointestinal (GI) and genitourinary (GU) toxicity in patients treated for adenocarcinoma of the prostate (ACP) using volumetric modulated arc therapy (VMAT).Methods and MaterialsA total of 122 (71 IMRT and 51 VMAT) ACP patients treated from 2004 to 2011 with definitive external beam radiation therapy were analyzed. Dose-volume histogram endpoints (V40, V65, V70, and V75 of the bladder and rectum) were collected for each patient. Median follow-up for patients treated with VMAT was 269 days versus IMRT was 1121 days. Acute Common Toxicity Criteria for Adverse Events (CTCAE) GI and GU toxicity scores, obtained during each weekly treatment check, were compared across cohorts. The univariate (UV) association between the covariates and outcomes was assessed and multivariable (MV) cumulative logit models were fit for each outcome.ResultsMedian patient age was 68 years and median prostate-specific antigen was 8.3. Both bladder and rectal V40, V65, V70, and V75 were all higher in the IMRT group versus the VMAT group (P < .05), which was likely influenced by larger planning target volumes in the IMRT group. The VMAT group had significantly lower rates of acute GU and acute GI CTCAE toxicity on UV association analysis. On MV analysis, VMAT remained independently associated with acute GU (odds ratio [OR], 0.18; 95% confidence interval [CI], 0.07-0.44; P < .001) and GI (OR, 0.16; 95% CI, 0.07-0.41; P < .001) toxicity.ConclusionsVMAT appears to be independently associated with lower rates of acute GI and GU toxicity when compared with traditional IMRT. Further exploration of toxicity improvements associated with VMAT use in the definitive treatment of ACP is needed.     

胃食管交界腺癌术后静态IMRT、VMAT和HT剂量学比较

目的 评价胃食管交界腺癌根治术后不同照射技术对靶区和正常组织剂量分布的影响,为临床治疗方法提供优选方案。方法 对 9例行根治性食管近端胃切除术或全胃切除术后的胃食管交界腺癌患者分别进行5个野静态IMRT、双弧VMAT和HT计划设计,通过DVH评价不同照射技术对靶区CI、HI和对OAR受量影响。放疗剂量45 Gy (1.8 Gy/次),同期每天口服替吉奥80 mg/m²,放疗日分2次口服。结果 HT靶区CI和HI好于IMRT和VMAT。对肠道和骨髓保护HT亦优于IMRT和VMAT。VMAT左肾 V₂₀、V₃₀和心脏 V₃₀低于IMRT和HT,而IMRT双肺 V₅、V₁₀较低;V₂₀和 D_mean三种技术差异不大。子野跳数平均数VMAT相似文献