食管癌三维适形调强放疗中放射性肺损伤相关因素

目的 探讨中下段食管癌三维适形调强放疗中放射性肺损伤的相关因素,为食管癌放疗的选择提供依据。方 法  选取本院2011 年 5 月至2014 年 5 月治疗的72 例食管癌患者,应用美国瓦里安直线加速器Ix-6074、Eclipse 11 放疗计 划系统制作计划,处方剂量（60~68）Gy/（30~34）F,95% 计划靶区达到处方剂量前提下,用剂量体积直方图比较肺组 织受照射时剂量体积与放射性肺损伤的关系,并探讨临床因素与放射性肺损伤的相关性。结果  随访发现1 年总生存率为 94.44%。中下段食管癌患者的肿瘤病变长度、伴有 COPD 及放疗总剂量与IMRT 后放射性肺损伤发生相关。72 例患者中9 例发生放射性肺损伤（12.50%）,V10、V15、V20、V30、肺Dmean 在放射性肺损伤与未发生放射性肺损伤患者中相比较 有显著性差异（均P＜0.05）,而 V5、V25、V35、V40、肺 Dmax和肺Dmin在两组间相比无显著性差异（均P＞0.05）。 结论  V10、V15、V20、V30、肺Dmean 剂量是放射性肺损伤发生的关键因素,食管癌三维适形调强放疗中放射剂量学因 素可较好预测放射性肺损伤发生。     

食管癌术后调强放疗致放射性肺损伤的相关因素分析

目的 探讨食管癌术后调强放疗致放射性肺损伤的相关因素.方法 回顾性分析采用调强放疗的65例食管癌术后患者的相关临床资料.患者给予计划靶区37.5 ～60 Gy/19～ 30 W2 Gy的处方剂量.行同步化疗的患者采取TP方案(紫杉醇+顺铂),观察年龄、性别、吸烟史、有无同步化疗以及放射物理参数V5、V10、V20、V30、Dmean与放射性肺损伤发生的相关性.结果 食管癌术后实行调强放疗的放射性肺损伤发生率为26.2％,年龄、性别、吸烟史和有无同步化疗与放射性肺损伤的发生无显著相关性(均P＞0.05),V5、V10、V20、V30、Dmean与放射性肺损伤的发生均显著相关(均P＜0.05).结论 食管癌术后放疗患者放射性肺损伤的发生与V5、V10、V.、V30、Dmean具有密切的相关性,在制定放疗计划时应考虑与放射性肺损伤有关的危险因素.     

利用PET-CT勾画食管癌靶区对放射性肺损伤的影响

目的:探讨CT扫描与PET-CT扫描在勾画食管癌靶区放疗后放射性肺损伤的差异。方法:利用PET-CT影像与同机的CT影像分别勾画14例胸中段食管癌患者的靶区体积,并利用Pinnacle3治疗计划系统分别计算出肺V20、V30和平均肺剂量;同期另15例胸中段食管癌患者由CT影像勾画靶区体积;并计算出肺V20、V30和平均肺剂量;29例患者放疗结束后3月、6月行CT扫描,计算放射性肺损伤的体积。结果:14例利用PET-CT勾画均小于利用同机CT勾画的靶区体积、肺V20、V30和平均肺剂量较小,放射性肺损伤发生率21%;另15例利用CT勾画的靶区体积、肺V20、V30和平均肺剂量较大,放射性肺损伤发生率40%,且放射性肺损伤体积大于利用PET-CT扫描在勾画食管癌靶区的患者。结论:利用PET-CT勾画食管癌放疗靶区优于CT,可减少放射性肺损伤。     

非小细胞肺癌IMRT放疗引起急性重症放射性肺损伤相关因素分析

目的:探讨调强适形放疗（IMRT）及同期化疗的非小细胞肺癌患者发生重度急性放射性肺损伤（SARP）的相关因素。方法:回顾性分析2010年1 月至2014年1 月天津医科大学肿瘤医院行IMRT 放疗及同期化疗的非小细胞肺癌患者临床资料,对影响SARP 发生的临床因素及剂量参数采用单因素和多因素分析。结果:共有2 323 例入组,其中1 241 例发生急性放射性肺损伤（ARP ）。 发生急性重症放射性肺损伤（SARP）患者共185 例,发生率为7.96% ;单因素分析发现性别、病理类型、放射总剂量、V 5（%）、平均剂量与SARP 发生率无关（P > 0.05）;而年龄> 60岁、FEV 1% 预计值、应用多西他赛+ 卡铂/ 顺铂化疗方案、V 20（%）、V 30（%）、双肺平均剂量（MLD ）等与SARP 发生率有关,且差异具有统计学意义（P < 0.05）。 经多因素分析显示年龄＞60岁、应用多西他赛+ 卡铂/ 顺铂化疗方案、V 20（%）、V 30（%）等与SARP 发生率显著相关（P < 0.05）,是SARP 发生率的独立影响因素。结论:对非小细胞肺癌患者行IMRT 及同步化疗时,应对高龄及患者多西他赛+ 铂类化疗方案患者和V 20、V 30高剂量的患者,采取必要的预防和治疗措施,减少SARP 的发生,提高患者的生存质量,减少因呼吸衰竭而引起死亡。      

肺癌同期放化治疗中放射性肺损伤的相关因素分析

 目的 观察三维适形放疗联合同期化疗治疗局部晚期非小细胞肺癌中放射性肺损伤情况,对其相关因 素进行分析,寻找合理的预测性 指标。 方法 47例符合入组条件的非小细胞肺癌患者接受三维适形放疗及同期化疗。处方剂量为60Gy常规 放疗,同期化疗方案为NP方案,对三维适形治疗计划及临床资料进行单因素、多因素分析,评 价肺损伤情况。 结果 （1）完全缓解3例, 部分缓解42例,总有效率为95.74%,1年生存率75.78%。全组发生急性放 射性肺炎0级2例,1级20 例,2级17例,3级8例,无4级放射性肺炎发生。（2）与严重放射性肺炎发生呈正相关的剂量 学因素为MLD、肺NTCP,肺V5、 V15、V20。临床资料中仅发现肿瘤GTV与严重放射性肺炎发生相关;多因素分析显示全肺平均 剂量为放射性肺炎的独立影 响因素。 结论 剂量学因素（MLD、肺NTCP,肺V5、V15、V20）可以较好地预测严重放射性肺炎的发生,全肺 平均剂量是放射性肺炎发生的独立影响因素。     

老年食管癌放疗致放射性肺炎相关因素分析

目的探讨老年食管癌患者三维适形放疗后放射性肺炎(RP)发生的相关因素。方法回顾性分析行三维适形放疗的90例老年食管癌患者的临床资料及放疗物理参数。结果 15例患者出现RP;RP相关因素有慢性阻塞性肺病(COPD)、再程放疗、放疗剂量、照射野数、肺V5、V10、V15、V20、V25、V30、V40等;性别、吸烟史、糖尿病、临床分期与RP的发生无关。结论 V10、V15、V20、MLD和COPD是RP的独立危险因素。     

造影剂对食管癌调强放疗计划的影响

目的探讨增强造影剂对食管癌调强放疗计划的影响。方法对10例食管癌进行CT平扫与增强造影,分别设计调强放疗计划,比较2个计划靶区剂量分布和危及器官的剂量体积受量。结果增强影像计划的靶区最大剂量、最小剂量、平均剂量及中位剂量,较平扫影像计划的平均高30 cGy,适形度指数和均匀性指数的比较无差异,增强影像计划的双肺平均剂量、心脏平均剂量受量高。2种计划的双肺V20、V30和脊髓最大剂量比较无差异。结论造影剂对食管癌调强放疗剂量有影响,但影响较小,可以直接在增强影像上设计放疗计划。     

三维适形放疗治疗食管癌致放射性肺炎的相关因素分析

目的探讨三维适形放疗治疗食管癌导致放射性肺炎的相关因素。方法根据放射性肺炎发性情况,将217例接受三维适形放疗治疗的食管癌患者分为放射性肺炎组和非放射性肺炎组,对比两组患者相关临床指标及放疗剂量学指标,探讨其相关因素。结果 217例患者中,发生放射性肺炎61例(28.1%),非放射性肺炎156例(71.9%),其中≥60岁者放射性肺炎发生率为36.7%,显著高于<60岁者,(21.0%,P<0.05)。放射性肺炎与非放射性肺炎患者在性别、年龄、病理类型、临床分期、肿瘤位置、是否吸烟、是否化疗、肺部合并症、V35、V40、V45的Vdose以及大体肿瘤体积(GTV)等方面差异均无统计学意义(P>0.05),而在V5、V10、V13、V15、V20、V25、V30的Vdose以及全肺平均剂量(LMD)、双肺容积等方面差异有统计学意义(P<0.01)。结论食管癌三维适形放疗计划的制定中需综合考虑剂量体积、全肺平均剂量以及双肺功能,以降低对肺组织的损伤以及放射性肺炎的发生率。     

80岁以上老年食管鳞癌调强放疗致放射性肺损伤的影响因素

目的  探讨80岁以上老年食管鳞癌调强放疗致放射性肺损伤（radiation-induced lung injury,RILI）的影响因素。方法  回顾性分析2014年5月至2016年10月在我院接受调强放疗的94例80岁以上老年食管鳞癌患者的临床资料,采用多因素Logistic回归分析RILI发生的影响因素。结果  94例患者RILI发生率为24.5%（23/94）,单因素分析显示吸烟史、肺部有基础疾病、双肺V₅和双肺V20与RILI发生有关（P<0.05）。多因素分析显示V₅≤55%是RILI的保护因素（OR=0.072,95%CI：0.017~0.308,P<0.001）,肺部有基础疾病是发生RILI的危险因素（OR=11.289,95%CI：2.186~58.312,P=0.004）。结论 80岁以上食管鳞癌患者调强放疗致放射性肺损伤的发生率较高,肺部有基础疾病可增加放射性肺损伤的发生风险,控制双肺V₅≤55%可有效减少RILI的发生。     

非小细胞肺癌三维适形放疗放射性肺损伤剂量学因素分析

目的 观察非小细胞肺癌三维适形放疗患者急性放射性肺炎的发生情况,并分析其与各剂 量学因素的关系。方法 收集2010年6月—2010年12月间首程行三维适形放疗的非小细胞肺癌患者68 例。从治疗计划系统的剂量体积直方图中获取以下剂量学参数：处方剂量、平均肺剂量(MLD)、正常 肺体积剂量（V5~V50间隔5 Gy）等,分别采用单因素及多因素分析各个剂量学参数与放射性肺炎之 间的关系,并采用受试者工作特征曲线寻找预测界值。结果 V5是放射性肺炎发生的独立预后因素 （χ2=5.15,P=0.023）。患者肺脏的V5超过57%时放射性肺炎的发生率可能会增加。结论 临床医师 在审核治疗计划时,除了要考虑V20、V30、MLD等常用参数外,还应关注V5的大小。     

Fatal pneumonitis associated with intensity-modulated radiation therapy for mesothelioma

PURPOSE: To describe the initial experience at Dana-Farber Cancer Institute/Brigham and Women's Hospital with intensity-modulated radiation therapy (IMRT) as adjuvant therapy after extrapleural pneumonectomy (EPP) and adjuvant chemotherapy. METHODS AND MATERIALS: The medical records of patients treated with IMRT after EPP and adjuvant chemotherapy were retrospectively reviewed. IMRT was given to a dose of 54 Gy to the clinical target volume in 1.8 Gy daily fractions. Treatment was delivered with a dynamic multileaf collimator using a sliding window technique. Eleven of 13 patients received heated intraoperative cisplatin chemotherapy (225 mg/m(2)). Two patients received neoadjuvant intravenous cisplatin/pemetrexed, and 10 patients received adjuvant cisplatin/pemetrexed chemotherapy after EPP but before radiation therapy. All patients received at least 2 cycles of intravenous chemotherapy. The contralateral lung was limited to a V20 (volume of lung receiving 20 Gy or more) of 20% and a mean lung dose (MLD) of 15 Gy. All patients underwent fluorodeoxyglucose positron emission tomography (FDG-PET) for staging, and any FDG-avid areas in the hemithorax were given a simultaneous boost of radiotherapy to 60 Gy. Statistical comparisons were done using two-sided t test. RESULTS: Thirteen patients were treated with IMRT from December 2004 to September 2005. Six patients developed fatal pneumonitis after treatment. The median time from completion of IMRT to the onset of radiation pneumonitis was 30 days (range 5-57 days). Thirty percent of patients (4 of 13) developed acute Grade 3 nausea and vomiting. One patient developed acute Grade 3 thrombocytopenia. The median V20, MLD, and V5 (volume of lung receiving 5 Gy or more) for the patients who developed pneumonitis was 17.6% (range, 15.3-22.3%), 15.2 Gy (range, 13.3-17 Gy), and 98.6% (range, 81-100%), respectively, as compared with 10.9% (range, 5.5-24.7%) (p = 0.08), 12.9 Gy (range, 8.7-16.9 Gy) (p = 0.07), and 90% (range, 66-98.3%) (p = 0.20), respectively, for the patients who did not develop pneumonitis. CONCLUSIONS: Intensity-modulated RT treatment for mesothelioma after EPP and adjuvant chemotherapy resulted in a high rate of fatal pneumonitis when standard dose parameters were used. We therefore recommend caution in the utilization of this technique. Our data suggest that with IMRT, metrics such as V5 and MLD should be considered in addition to V20 to determine tolerance levels in future patients.     

Hybrid IMRT for treatment of cancers of the lung and esophagus

PURPOSE: To report on a hybrid intensity-modulated radiation therapy (IMRT; static plus IMRT beams treated concurrently) technique for lung and esophageal patients to reduce the volume of lung treated to low doses while delivering a conformal dose distribution. METHODS: Treatment plans were analyzed for 18 patients (12 lung and 6 esophageal). Patients were treated with a hybrid technique that concurrently combines static (approximately two-thirds dose) and IMRT (approximately one-third dose) beams. These plans were compared with conventional three-dimensional (3D; non-IMRT) plans and all IMRT plans using custom four- and five-field arrangements and nine equally spaced coplanar beams. Plans were optimized to reduce V13 and V5 values. Dose-volume histograms were calculated for the planning target volume, heart, and the ipsilateral, contralateral, and total lung. Lung volumes V5, V13, V20, V30; mean lung dose (MLD); and the generalized equivalent uniform dose (gEUD) were calculated for each plan. RESULTS: Hybrid plans treated significantly smaller total and contralateral lung volumes with low doses than nine-field IMRT plans. Largest reductions were for contralateral lung V5, V13, and V20 values for lung (-11%, -15%, -7%) and esophageal (-16%, -20%, -7%) patients. Smaller reductions were found also for 3D and four- and five-field IMRT plans. MLD and gEUDs were similar for all plan types. The 3D plans treated much larger extra planning target volumes to prescribed dose levels. CONCLUSIONS: Hybrid IMRT demonstrated advantages for reduction of low-dose lung volumes in the thorax for reducing low dose to lung while also reducing the potential magnitude of dose deviations due to intrafraction motion and small field calculation accuracy.     

食管癌螺旋断层放疗及三维适形调强放疗计划剂量学研究

目的 近年来放射治疗设备不断更新,放疗技术持续发展,肿瘤放疗方式有了更多的选择.本研究通过评估食管癌的螺旋断层放疗(tomotherapy, TOMO)及三维适形调强放疗(intensity modulation radiation therapy, IMRT)的剂量学特性,为临床上食管癌放疗方式的选择提供依据.方法 选取2014-07-13-2015-02-25浙江省肿瘤医院胸部肿瘤放疗科10例食管癌患者,勾画靶区及正常器官后,分别传输至Raystation及TOMO计划系统,给予肿瘤原发灶(PGTV)61.6 Gy/28次,计划靶区(PTV)56.0 Gy/28次,根据RTOG 1106标准限制危及器官(organs at risk, OAR)剂量.分别对靶区的剂量体积直方图(dose volume histogram, DVH)、均匀性指数(homogeneity index, HI)、适形性指数(conformal index CI)和OAR(肺、心脏、脊髓)受照最大剂量及平均剂量进行评估.结果 两种计划都能满足处方剂量要求和危及器官受量限制.TOMO计划中PGTV的中位均匀性指数(HI)为0.057 5,优于IMRT计划的0.073 5, P=0.047.TOMO计划中PTV的中位适形性指数(CI)为0.785,优于IMRT计划的0.682 5, P=0.009.TOMO计划中PGTV的中位最大剂量Dmax为64.9 Gy,明显低于IMRT计划的66.5 Gy, P=0.005;TOMO计划中PTV的中位最大剂量Dmax为64.1 Gy,明显低于IMRT计划的64.9 Gy, P=0.028. TOMO计划的中位总的肺剂量为10.8 Gy,低于IMRT计划的11.9 Gy, P=0.005.TOMO计划的中位总的心脏剂量为22.6 Gy,明显低于IMRT计划的24.3 Gy, P=0.028. TOMO计划的中位脊髓最大剂量为40.2 Gy,明显低于IMRT计划的41.7 Gy, P=0.007.结论 食管癌放疗中TOMO放疗计划对比IMRT放疗计划,具有更好的靶区覆盖适形性及剂量分布均匀性,同时明显减少双肺、心脏及脊髓的受照剂量.     

Dose-volume histogram analysis as predictor of radiation pneumonitis in primary lung cancer patients treated with radiotherapy

PURPOSE: To determine the relationship between various parameters derived from lung dose-volume histogram analysis and the risk of symptomatic radiation pneumonitis (RP) in patients undergoing radical radiotherapy for primary lung cancer. METHODS AND MATERIALS: The records of 156 patients with lung cancer who had been treated with radical radiotherapy (>/=45 Gy) and for whom dose-volume histogram data were available were reviewed. The incidence of symptomatic RP was correlated with a variety of parameters derived from the dose-volume histogram data, including the volume of lung receiving 10 Gy (V(10)) through 50 Gy (V(50)) and the mean lung dose (MLD). RESULTS: The rate of RP at 6 months was 15% (95% confidence interval 9-22%). On univariate analysis, only V(30) (p = 0.036) and MLD (p = 0.043) were statistically significantly related to RP. V(30) correlated highly positively with MLD (r = 0.96, p < 0.001). CONCLUSION: V(30) and MLD can be used to predict the risk of RP in lung cancer patients undergoing radical radiotherapy.     

肺低剂量区体积预测急性放射性肺炎价值探讨

目的 观察胸部肿瘤三维适形放疗患者放射性肺炎发生情况,分析其与各临床、剂量学因素关系,探讨低剂量区体积对放射性肺炎的预测价值.方法 2005-2008年本科收治的中晚期非小细胞肺癌(NSCLC)及食管癌患者共161例接受了三维适形放疗,其中局部晚期NSCLC患者53例,处方剂量60 Gy分30～34次,均行长春瑞滨+顺铂同期化疗;食管癌患者108例,处方剂量58～70 Gy分29～35次,单纯放疗46例,余62例接受亚叶酸钙+氟尿嘧啶+顺铂同期化疗.对急性放射性肺炎进行Spearman等级相关分析、Logistic因素分析及受试者工作特征(ROC)曲线分析.结果 随访率100%.全组急性放射性肺炎总发生率为57.8%(93例),其中NSCLC组为94%(50例,4、5级各1例),食管癌组为39.8%(43例,无≥4级病例).等级相关分析结果显示患者性别(r=0.19,P=0.016)、大体肿瘤体积(r=0.52,P=0.000))、平均肺剂量(r=0.33,P=0.000)、肺正常组织并发症概率(r=0.30,P=0.000)、接受5、10、15、20、25、30 Gy照射的肺体积百分比(肺V5～V30,r=0.21～0.29,P=0.000～0.027)均与放射性肺炎发生相关.Logistic因素分析结果显示肺V5(X2=7.07,P=0.008)、大体肿瘤体积(X2=10.21,P=0.001)是预测≥2级放射性肺炎最有价值指标.ROC曲线分析结果显示曲线下面积为0.684,P=0.000;曲线界值为V5=55%.肺V5≥55%组与<55%组≥2级放射性肺炎发生率分别为43%(36/84)和18%(14/77).结论 平均肺剂量、正常组织并发症概率、V5～V30可较好预测放射性肺炎的发生,其中V5可能是最有价值的预测性指标.当V5>55%时≥2级的急性放射性肺炎的发生率可能会明显增加,制定治疗计划时除平均肺剂量、V20、V30外,还应将低剂量区体积限制在适当范围内.     

The risk of early and late lung sequelae after conformal radiotherapy in breast cancer patients

PURPOSE: To study the risks of early and late radiogenic lung damage in breast cancer patients after conformal radiotherapy. METHODS AND MATERIALS: Radiogenic lung sequelae were assessed prospectively in 119 patients by means of clinical signs, radiologic abnormalities, and the mean density change (MDC) of the irradiated lung on CT. RESULTS: Significant positive associations were detected between the development of lung abnormalities 3 months or 1 year after the radiotherapy and the age of the patient, the ipsilateral mean lung dose (MLD), the radiation dose to 25% of the ipsilateral lung (D(25%)) and the volume of the ipsilateral lung receiving 20 Gy (V(20 Gy)). The irradiation of the axillary and supraclavicular lymph nodes favored the development of pneumonitis but not that of fibrosis. No relation was found between the preradiotherapy plasma TGF-beta level and the presence of radiogenic lung damage. At both time points, MDC was strongly related to age. Significant positive associations were demonstrated between the risks of pneumonitis or fibrosis and the age of the patient, MLD, D(25%), and V(20 Gy). A synergistic effect of MLD, D(25%), and V(20 Gy) with age in patients older than 59 years is suggested. CONCLUSION: Our analyses indicate that the risks of early and late radiogenic lung sequelae are strongly related to the age of the patient, the volume of the irradiated lung, and the dose to it.     

CT/CT图像融合技术评价食管癌二程放疗的可靠性研究

目的:探讨利用CT/CT图像融合技术来评价食管癌二程放疗的准确性和可靠性。方法:9例食管癌患者,接受调强放疗46Gy后,行二次CT定位,制定后程适形或调强计划,给予处方剂量20Gy。将两次CT图像融合得到全程融合计划,总处方剂量66Gy。比较两个疗程危及器官的体积变化,将首程计划移植到二次定位图像上,计算并比较危及器官受照剂量的差别;将一程计划和二程计划的危及器官评价结果直接相加,与融合计划进行比较。结果:两次定位肺与心脏的体积变化差异无统计学意义(P>0.05);CT/CT融合精度对肺和心脏的受量评价差异无统计学意义(P>0.05),而对于脊髓最大受照剂量差异具有统计学意义(P<0.05);分次计划评价指标相加与融合计划的比较结果是,双侧肺V20、心脏V30的差异有统计学意义(P<0.05),双侧肺平均受照剂量和脊髓的最大受照剂量差异无统计学意义(P>0.05)。结论:在食管癌分程放疗中,宜采用融合计划来评价肺和心脏的受照剂量,可以采用两次计划分别评价得出的脊髓最大受照剂量之和来作为全程脊髓最大受量的评价指标。     

Intensity-modulated radiotherapy for resected mesothelioma: the Duke experience

PURPOSE: To assess the safety and efficacy of intensity-modulated radiotherapy (IMRT) after extrapleural pneumonectomy for malignant pleural mesothelioma. METHODS AND MATERIALS: Thirteen patients underwent IMRT after extrapleural pneumonectomy between July 2005 and February 2007 at Duke University Medical Center. The clinical target volume was defined as the entire ipsilateral hemithorax, chest wall incisions, including drain sites, and involved nodal stations. The dose prescribed to the planning target volume was 40-55 Gy (median, 45). Toxicity was graded using the modified Common Toxicity Criteria, and the lung dosimetric parameters from the subgroups with and without pneumonitis were compared. Local control and survival were assessed. RESULTS: The median follow-up after IMRT was 9.5 months. Of the 13 patients, 3 (23%) developed Grade 2 or greater acute pulmonary toxicity (during or within 30 days of IMRT). The median dosimetric parameters for those with and without symptomatic pneumonitis were a mean lung dose (MLD) of 7.9 vs. 7.5 Gy (p = 0.40), percentage of lung volume receiving 20 Gy (V(20)) of 0.2% vs. 2.3% (p = 0.51), and percentage of lung volume receiving 5 Gy (V(20)) of 92% vs. 66% (p = 0.36). One patient died of fatal pulmonary toxicity. This patient received a greater MLD (11.4 vs. 7.6 Gy) and had a greater V(20) (6.9% vs. 1.9%), and V(5) (92% vs. 66%) compared with the median of those without fatal pulmonary toxicity. Local and/or distant failure occurred in 6 patients (46%), and 6 patients (46%) were alive without evidence of recurrence at last follow-up. CONCLUSIONS: With limited follow-up, 45-Gy IMRT provides reasonable local control for mesothelioma after extrapleural pneumonectomy. However, treatment-related pulmonary toxicity remains a significant concern. Care should be taken to minimize the dose to the remaining lung to achieve an acceptable therapeutic ratio.     

Feasibility of using intensity-modulated radiotherapy to improve lung sparing in treatment planning for distal esophageal cancer.

BACKGROUND AND PURPOSE: To evaluate the feasibility whether intensity-modulated radiotherapy (IMRT) can be used to reduce doses to normal lung than three-dimensional conformal radiotherapy (3 DCRT) in treating distal esophageal malignancies. PATIENTS AND METHODS: Ten patient cases with cancer of the distal esophagus were selected for a retrospective treatment-planning study. IMRT plans using four, seven, and nine beams (4B, 7B, and 9B) were developed for each patient and compared with the 3 DCRT plan used clinically. IMRT and 3 DCRT plans were evaluated with respect to PTV coverage and dose-volumes to irradiated normal structures, with statistical comparison made between the two types of plans using the Wilcoxon matched-pair signed-rank test. RESULTS: IMRT plans (4B, 7B, 9B) reduced total lung volume treated above 10 Gy (V(10)), 20 Gy (V(20)), mean lung dose (MLD), biological effective volume (V(eff)), and lung integral dose (P<0.05). The median absolute improvement with IMRT over 3DCRT was approximately 10% for V(10), 5% for V(20), and 2.5 Gy for MLD. IMRT improved the PTV heterogeneity (P<0.05), yet conformity was better with 7B-9B IMRT plans. No clinically meaningful differences were observed with respect to the irradiated volumes of spinal cord, heart, liver, or total body integral doses. CONCLUSIONS: Dose-volume of exposed normal lung can be reduced with IMRT, though clinical investigations are warranted to assess IMRT treatment outcome of esophagus cancers.