卡瑞利珠单抗结合SBRT对晚期寡转移非小细胞肺癌患者血清肿瘤标志物水平的影响

目的:针对晚期寡转移非小细胞肺癌患者采取卡瑞利珠单抗与立体定向体部放疗(SBRT)联合治疗,分析其疗效。方法:起止时间:2020年4月,终止时间:2023年4月,选取我院该阶段参与治疗的晚期寡转移非小细胞肺癌患者作为对象,共计120人,分设为对照组、观察组各60人。对照组予以SBRT治疗,观察组SBRT联合卡瑞利珠单抗治疗。观察两组治疗效果。结果:治疗后,观察组临床疗效高于对照组,P<0.05;从毒副反应发生情况上看,观察组放射性肺炎发生率低于对照组,P<0.05;从血清肿瘤标志物水平上看,观察组癌胚抗原、鳞状细胞癌抗原、细胞角蛋白19片段抗21-l均较对照组低,P<0.05。结论:SBRT与卡瑞利珠单抗结合治疗,可提高临床治疗效果,降低毒副反应,使血清肿瘤标志物指标水平下降,效果较好。

测量治疗床、SBRT体架及DAVID系统造成的剂量衰减

目的:通过测量6 MV的X线经过治疗床、SBRT体架和DAVID系统后的剂量衰减,为计划设计时的剂量补偿提供参考数据。方法:加速器与固体水之间无任何器材,源皮距(SDD)为100 cm,出束照射100 MU,利用电离室测量固体水下深度5 cm的剂量,作为基准剂量。同样条件下测量治疗床、SBRT体架和DAVID系统以不同组合在水下深度5 cm的剂量。结果:射线穿过治疗床剂量衰减了3.08%,经过治疗床和SBRT体架衰减了13.10%,经过治疗床、SBRT体架和DAVID系统衰减了13.10%,经过治疗床和DAVID系统衰减了10.88%,经过DAVID系统衰减8.07%。结论:在没有安装DAVID系统时,只有经过治疗床和SBRT体架的射线需要进行剂量补偿。安装了DAVID系统时,所有的射线束都需要计算DAVID系统对射线的衰减,经过治疗床和SBRT体架的射线还需要计算这两个器材对剂量的衰减。不同情况下衰减比例不同,需要补偿的剂量也不同。

CT引导下在肝脏中单针植入双金标用于射波刀SBRT治疗

目的为了提高植入效率,减少植入时间以及金标植入带来的痛苦和风险,我们在CT引导下一针植入一颗金标的技术基础上开发了一针植入双金标技术。方法 2011年8月-2012年7月间共有429例肝脏肿瘤患者在射波刀治疗前采用单针双金标技术植入1252颗金标,年龄最小19岁,年龄最大74岁。单针双金标技术是在单针单金标技术的基础上,一次穿刺植入2颗金标。首先利用CT获取肿瘤的影像,确定第一颗金标植入的深度和角度,利用18-G针把第一颗金标植入到指定位置;针芯与针套缓慢拔出3-5cm,并在原位置停留3-5min,然后放入第二颗金标。金标植入完成后,获取金标影像,测量两颗金标之间的距离和连线角度,检查是否符合金标植入原则。结果单针双金标技术植入的1252颗金标中,有18颗(1.44%)金标间距<20 mm,有24颗(1.92%)金标在45°角方向共线,有17颗(1.04%)金标移位到其它器官,成功率达到95.28%。1252颗金标通过单针双金标技术只需要植入626次,效率提高了一倍,穿刺次数减少了一半。结论单针双金标技术使植入效率提高1倍,同时由于穿刺次数减半,不仅降低了成本,也减少了穿刺带来的风险。金标间距<20 mm和45°共线是影响成功率的关键因素,我们需要掌握该技术的操作要点,否则会造成植入金标无法使用。

周围型肺癌无均整滤过器模式SBRT的剂量学研究

目的:评价动态适形拉弧(DCA)和容积旋转(RA)两种体部立体定向放射治疗(SBRT)技术在早期周围型非小细胞肺癌治疗中的剂量学差异。方法:选取15例早期周围型非小细胞肺癌患者,进行4D-CT扫描,按照美国放射治疗肿瘤学组(RTOG)标准勾画靶区和危及器官(OAR)。在Eclipse 10.0治疗计划系统中分别设计基于DCA技术和RA调强技术的体部立体定向放射治疗计划。采用TrueBeam加速器无均整滤过器6 MV X射线,剂量率为1400 MU/min,处方剂量为48 Gy,分4次治疗。计划设计中的靶区剂量覆盖和OAR限量要求均按RTOG标准执行。评价靶区90%、95%和100%处方剂量覆盖的体积(V_(90%)、V_(95%)和V_(100%))、适形性指数(CI)、均匀性指数(HI)、距离靶区2 cm处任意方向的最大剂量的百分数(D_(2cm))、50%处方剂量的等剂量线所包绕的体积与靶区体积的比值(R_(50%))、OAR受照剂量的最大值(D_(max))以及机器跳数及计划设计时间。结果:DCA和RA计划的靶区剂量覆盖的差异和OAR受照剂量的差异均无统计学意义,计划设计的要求均能满足RTOG标准。DCA和RA计划靶区的CI分别为1.45±0.16和1.06±0.02,差异有统计学意义(t=6.543,P<0.05),HI的比较差异无统计学意义。两种计划的D_(2cm)、R_(50%)、MU和计划设计时间比较差异均有统计学意义(t=6.267,t=8.151,t=6.037,t=6.316;P<0.05)。结论:DCA和RA计划对OAR的保护无差别,但RA计划的适形性优于DCA计划。DCA计划显著的降低了机器跳数和减少了计划设计时间。

影响肺癌SBRT肿块运动幅度的因素及进行4DCT扫描的必要性研究

目的 基于四维CT（4DCT）扫描得到的不同时相图像,以期探讨进行立体定向体部放射治疗（SBRT）时进行4DCT扫描的必要性以及常规扫描的可行性.方法 收集2016年4月—2017年7月,19例拟进行SBRT的早期肺癌患者.分析所有患者10个时相胸部4DCT图像,得到呼吸频率;筛选出吸气末和呼气末图像,两者相减计算膈顶运动幅度;确定肿块的解剖位置、和胸壁粘连情况.分别得到肿块头脚、左右、腹背侧最大运动幅度,并求出肿瘤体积的变化.应用SPSS 16.0软件处理,寻找影响肿块三维方向运动因素,对于年龄、KPS评分、呼吸频率、膈顶运动幅度采用Spearman相关分析;对于性别、肿瘤部位、是否和胸壁粘连采用秩和检验.对单因素分析中差异有统计学意义的因素进行Logistic多元回归分析.结果19例患者肿块头脚、左右和腹背方向运动幅度分别为（3.32±2.67）mm,（0.21±0.33）mm,（0.20±0.18）mm.单因素分析结果：肿瘤部位、膈顶运动幅度影响肿块头脚运动幅度（P〈0.05）.所有因素对于左右和腹背方向运动幅度影响差异无统计学意义.多因素回归分析提示：肿块部位（P=0.001）、膈顶运动幅度（P=0.006）影响肿块运动幅度差异有统计学意义.肿块运动幅度与肿块部位、膈顶运动幅度具有相关性.结论 呼吸运动主要影响肿块的头脚方向运动,对腹背、左右方向运动可不考虑.位于肺上叶、和胸壁粘连的肺癌患者可不考虑肿块运动、肿瘤体积变化,可进行基于常规CT扫描的SBRT治疗.位于肺中叶和下叶的肿瘤进行SBRT治疗,采用4DCT扫描具有必要性.

锥形束CT引导下VMAT-SBRT治疗非小细胞肺癌肺部寡转移靶区边界和临床疗效及毒副反应

目的 探讨锥形束CT引导下VMAT-SBRT治疗非小细胞肺癌肺部寡转移的靶区边界和临床疗效及毒副反应。方法 收集2016年1月至2018年1月温州医科大学附属第一医院放疗中心VMAT-SBRT治疗的NSCLC肺部寡转移患者40例,56个寡转移灶,4DCT定位,55 Gy/5次,VMAT-SBRT隔天照射;每次治疗前CBCT获取校准前摆位误差,在线校正后再次CBCT获取校正后误差,SPSS 19.0统计分析校正前后误差,由扩边公式Mptv=2.5Σ+0.7δ计算临床靶区到计划靶区的外放边界。治疗结束后1、3、6、12、24个月和36个月复查增强CT,用实体瘤评价标准RECIST1.1评价疗效,用Kaplan-Meier法进行局部控制及生存分析,用RTOG的放射损伤标准评定急慢性毒副反应。结果 CBCT校正前后X、Y、Z方向靶区外扩边界,校正前:0.51 cm、0.65 cm、0.57 cm;校正后:0.24 cm、0.38 cm、0.27 cm。随访6~42个月,CR 22.5%、PR 60.0%、SD 10.0%和PD 7.5%,CR+PR 82.5%;1、2、3年的LC率为95%、84%和73%,1年、2年、3年的OS率为85%、68%、45%。放疗后急慢性毒副反应为放射性肺炎、放射性食管炎、放射性纤维化,均为0~2级,无3级及以上反应。结论 CBCT引导下靶区外扩边界明显缩小,VMAT-SBRT治疗NSCLC肺部寡转移毒副反应小,局部控制率和生存率高,疗效显著,是一种安全可靠的治疗方式。

非小细胞肺癌SBRT放疗剂量分布的研究

目的分别设计IMRT、VMAT和非共面VMAT三种放疗计划进行对比,以指导临床选择更优的SBRT治疗非小细胞肺癌(NSCLC)。方法 20例NSCLC患者,采用4D-CT定位获取定位图像,分别采用逆向调强(IMRT)、容积旋转调强(VMAT)和非共面容积旋转调强(N-VMAT)进行SBRT治疗计划的设计,比较计划靶区(PTV)和危及器官(OAR)的剂量分布图、剂量体积直方图(DVH)和机器的相关参数。结果对于靶区PTV的D_(2%)、D_(95%)、D_(50%)三种计划之间比较差异没有统计学意义(P>0.05)。靶区PTV的适形指数(CI),N-VMAT计划在剂量学的分布上整体优于IMRT计划和VMAT计划(P<0.05)。对于左肺的V_(5%)、V_(10%)、Dmean和右肺的V_(5%)、Dmean,N-VMAT计划在剂量学的分布上优于IMRT计划和VMAT计划(P<0.05)。结论 N-VMAT计划在剂量学的分布上整体优于IMRT计划和VMAT计划,它不仅有较好的靶区适形度和均匀度,而且有利于对肺组织的保护,可以为NSCLC患者的SBRT治疗提供理论参考。

锥形束CT引导下应用SBRT治疗早期非小细胞肺癌疗效观察

目的:评价锥形束CT(cone beam CT,CBCT)引导下应用立体定向放射治疗(stereotactic body radiation therapy,SBRT)治疗早期非小细胞肺癌的近期疗效及毒副反应。方法:选取17例I期非小细胞肺癌患者接受CBCT引导下的SBRT胸部放疗,SBRT处方剂量DT 60 Gy/12 f,5次/周,95%以上计划靶区(PTV)满足处方剂量,90%等剂量线包含整个靶区,严格控制各危及器官剂量:双肺V_5<50%、V_(20)<20%,脊髓D_(max)<25 Gy,心脏D_(mean)<27 Gy等。每次照射前均行CBCT扫描并在线匹配、校准。结果:所有患者均完成放疗并随访3~24个月(中位随访期18个月),其中完全缓解(CR)4例,部分缓解(PR)12例,稳定(SD)1例,无进展患者,总有效率为94.1%。1年局部控制率和生存率分别为100%和100%。2年局部控制率和生存率分别为88.2%和82.3%。放疗期间未出现III级以上严重的放射性毒副反应。结论:应用CBCT引导下行SBRT治疗早期非小细胞肺癌,可显著提高其局部控制率和生存率,毒副反应较轻,但其远期疗效及晚期毒副反应仍待进一步随访观察。

Verification and Dosimetric Impact of Acuros XB Algorithm for Stereotactic Body Radiation Therapy (SBRT) and RapidArc Planning for Non-Small-Cell Lung Cancer (NSCLC) Patients

Purpose: The experimental verification of the Acuros XB (AXB) algorithm was conducted in a heterogeneous rectangular slab phantom, and compared to the Anisotropic Analytical Algorithm (AAA). The dosimetric impact of the AXB for stereotactic body radiation therapy (SBRT) and RapidArc planning for 16 non-small-cell lung cancer (NSCLC) patients was assessed due to the dose recalculation from the AAA to the AXB. Methods: The calculated central axis percentage depth doses (PDD) in a heterogeneous slab phantom for an open field size of 3 ×3 cm2 were compared against the PDD measured by an ionization chamber. For 16 NSCLC patients, the dose-volume parameters from the treatment plans calculated by the AXB and the AAA were compared using identical jaw settings, leaf positions, and monitor units (MUs). Results: The results from the heterogeneous slab phantom study showed that the AXB was more accurate than the AAA;however, the dose underestimation by the AXB (up to ?3.9%) and AAA (up to ?13.5%) was observed. For a planning target volume (PTV) in the NSCLC patients, in comparison to the AAA, the AXB predicted lower mean and minimum doses by average 0.3% and 4.3% respectively, but a higher maximum dose by average 2.3%. The averaged maximum doses to the heart and spinal cord predicted by the AXB were lower by 1.3% and 2.6% respectively;whereas the doses to the lungs predicted by the AXB were higher by up to 0.5% compared to the AAA. The percentage of ipsilateral lung volume receiving at least 20 and 5 Gy (V20 and V5 respectively) were higher in the AXB plans than in the AAA plans by average 1.1% and 2.8% respectively. The AXB plans produced higher target heterogeneity by average 4.5% and lower plan conformity by average 5.8% compared to the AAA plans. Using the AXB, the PTV coverage (95% of the PTV covered by the 100% of the prescribed dose) was reduced by average 8.2% than using the AAA. The AXB plans required about 2.3% increment in the number of MUs in order to achieve the same PTV coverage as in the AAA plans. Conclusion: The AXB is more accurate to use for the dose calculations in SBRT lung plans created with a RapidArc technique;however, one should also note the reduced PTV coverage due to the dose recalculation from the AAA to the AXB.

准直器角度对肺癌SBRT-VMAT治疗计划的影响

目的:研究准直器角度对中央型非小细胞肺癌(NSCLC)患者体部立体定向放射治疗(SBRT)容积旋转调强(VMAT)计划剂量学影响。方法:选取10名中央型NSCLC患者进行VMAT计划设计。使用Varian Eclipse系统,6 MV FFF X射线,最大剂量率1400 MU/min。机架角度:CCW 179°~181°、CW 181°~179°,双弧准直器角度互组,0°~90°每间隔10°设置准直器角度,即为(0°,0°)、(10°,350°)、(20°,340°)、(30°,330°)、(40°,320°)、(50°,310°)、(60°,300°)、(70°,290°)、(80°,280°)和(90°,270°)制定十个计划。在处方剂量相同并且处方剂量线包绕相同靶区体积的前提下(归一至80%),比较计划靶区参数:D 95%、V 90%、适形度指数(CI)、梯度指数(GI)、D 2 cm以及机器跳数(MU),危及器官参数:双肺(D 1500 cm^(3)、D 1000 cm^(3))、心脏(D 15 cm^(3))、脊髓(D 1.2 cm^(3)、D 0.35 cm^(3))。用SPSS软件对每个分析指标做Wilcoxon符号秩检验,判断差异是否具有统计学意义。结果:在有统计学意义的基础上,10组计划中,准直器角度为60°时(P<0.05),靶区D 95%剂量最高,准直器角度为50°时(P<0.05),靶区V 90%最高。CI和GI在0°最佳。危及器官双肺(D 1500 cm^(3)、D 1000 cm^(3))、心脏(D 15 cm^(3))、脊髓(D 1.2 cm^(3))受照剂量均在0°最低,脊髓D 0.35 cm^(3)在整个角度范围内不具有统计学差异。此外,所有计划中危及器官受照剂量均远远低于计划规定值,其中双肺(D 1500 cm^(3))在50°的剂量与最低值仅相差4.1%(P<0.05),心脏(D 15 cm^(3))在60°的剂量与最低值仅相差3.4%(P<0.05)。结论:改变准直器角度对肺癌SBRT-VMAT计划剂量有明显的影响。选择合适的准直器角度,正常组织受照剂量远远低于计划限量时,靶区体积剂量明显提高,但计划复杂度也略有提升。在临床计划设计过程中,应充分考虑准直器角度的影响,制定更合适的治疗计划。

Feasibility Study on Deformable Image Registration for Lung SBRT Patients for Dose-Driven Adaptive Therapy

The purpose of the study was to evaluate a treatment dose using planning computed tomography (pCT) that was deformed to pre-treatment cone beam computed tomography (CBCT) for lung stereotactic body radiation therapy (SBRT) treatment. Five lung SBRT patients were retrospectively selected, and their daily CBCTs were employed in this study. Dosimetric comparison was performed between the original and recalculated plans from the deformed pCT (dose per fraction) by comparing a target coverage and organs at risk. Dose summation of five fractions was computed and compared to the original plan. A phantom study was conducted to evaluate the dosimetric accuracy for the dose per fraction. In the phantom study, the difference between the mean Hounsfield Unit (HU) values of the original and deformed pCTs is less than 0.5%. In patient study, the mean HU deviation of the five deformed pCTs compared to that of the original pCT was within ±5%, which is dosimetrically insignificant. While the internal target volume (ITV) shrank by 17% on average among the five patients, mean lung dose (MLD) increased by up to 7%, and D95% of PTV decreased slightly but stayed within 5%. Results showed that MLD might be a better indicative metric of normal lung dose than V20Gy as the ITV volume decreases. This study showed a feasibility to use a deformed pCT for evaluation of the dose per fraction and for a possible plan adaptation in lung SBRT cases. Readers should be cautious in selecting patients before clinical application due to the image quality of CBCT.

Dosimetric Comparisons of Lung SBRT with Multiple Metastases by Two Advanced Planning Systems

Purpose: To evaluate planning quality of Stereotactic body Radiotherapy (SBRT) with multiple lungmetastases generated by the Pinnacle and Tomotherapy planning systems, respectively. Methods and Materials: Nine randomly selected patients diagnosed with non-small cell lung carcinoma with multiple lesions were planned with Philips Pinnacle (version 9.2, Fitchburg, WI) and Tomotherapy (version 4.2, Madison, WI), respectively. Both coplanar and non-coplanar IMRT plans were generated on Pinnacle system. A total dose of 60 Gy was prescribed to cover 95% of Planning Target Volume (PTV) in 3 fractions based on the RTOG0236 protocol prescription [1]. All plans with single isocenter setting were used for multiple lesions planning. A set of nine static beams were used for Pinnacle plansusing Direct Machine Parameters Optimization (DMPO) algorithm of RTOT0236 dose constraints. Planning outcomes such as minimum and mean doses, V95, D95 (95% of target volume receivesprescription dose), D5, and D1 to PTV, maximum dose to heart, esophagus, cord, trachea, brachial plexus, rib, chest wall, and liver, mean dose toliver, total lung, right and left lung, volume of chest wall receives 30 Gy, volume of lungs receives 5 Gy and 20 Gy (V5 and V20), conformity index (CI) and heterogeneity index (HI) were all reported for evaluation. Results: Mean volume of PTV was 37.77 ± 23.4 cm3. D95 of PTV with Tomotherapy, coplanar, non-coplanar plan was 60.2 ± 0.3 Gy, 58.6 ± 1.2 Gy, and 59.1 ± 0.7 Gy, respectively. Mean dose to PTV was lower for Tomotherapy (p 5 (p 1 (p = 0.001). CI was higher with Tomotherapyplans (p p 5 which needs more attention for toxicity analysis.

SBRT临床应用结果的思考

体部立体定向放射治疗(Stereotactic Body Radiation Therapy,SBRT)是应用立体定位技术和特殊射线装置,将多源、多线束或多野三维空间聚焦的高能射线聚焦于体内某一靶区,使病灶组织受到高剂量照射,周围正常组织受量减少,从而获得临床疗效高,副作用小的一类放疗技术的总称,采用γ射线所完成的SBRT简称为γ刀,采用X射线所完成的SBRT简称为X刀。SBRT的优势是采用高分次剂量、短疗程分割模式,具有明显的放射生物学优势。无论是国外还是国内,SBRT治疗肿瘤的临床结果均令人鼓舞,治疗早期非小细胞肺癌的3年生存率和局控率均优于常规放疗,与手术效果无差异,而且副作用小,治疗肝癌和胰腺癌的局控率和生存率也获得了大幅度提高。我国的γ刀技术具有独特的剂量聚焦优势和完全自主知识产权,符合我国"十一五"科技自主创新的要求,而且疗效显著、性价比高、易于推广应用符合我国国情。但由于种种原因,SBRT技术在中国尚未引起足够重视,中国γ刀技术需要从设备完善、加大政府支持力度和规范临床应用三个方面进行改进,SBRT的健康发展对推动我国放射肿瘤专业发展具有重要意义。

SBRT在NSCLC中的疗效、安全性及成本-效果分析

目的:探究医用直线加速器立体定向放射治疗(stereotactic body radiotherapy,SBRT)在晚期非小细胞肺癌(NSCLC)中的疗效、安全性,并行成本-效果分析。方法:回顾性分析122例接受放射治疗的晚期NSCLC患者临床资料,根据放射治疗方法分为SBRT组(58例)及调强适形放射治疗(intensity-modulated radiotherapy,IMRT)组(64例),比较两组临床疗效、主要器官受照剂量及放射不良反应发生情况,并行成本-效果分析。结果:两组临床疗效、主要器官受照剂量及放射不良反应发生情况比较,差异均无统计学意义(P>0.05),但SBRT组成本-效果比低于IMRT组(P<0.05)。结论:SBRT与IMRT治疗晚期NSCLC疗效与安全性相当,但SBRT更具经济学优势。

联合ExactTrac X-Ray与Cone Beam CT在NSCLC-SBRT中的应用分析

目的探讨应用ExactTrac x-Ray(ETX)与Cone Beam CT(CBCT)分析非小细胞肺癌立体定向放疗(NSCLC-SBRT)中分次间及分次内的误差差异。方法随机选取22例行SBRT的NSCLC患者,所有患者治疗前行CBCT扫描,图像配准范围为肺部肿块并兼顾胸腔轮廓与脊柱等骨性标记,获得移位误差后进行修正并开始治疗。在治疗开始及结束分别选择0°与1800进行2次ETX拍片验证(ETX-0,etx-180),从而获得分次内移位误差,图像配准范围为胸腔轮廓及脊柱等骨性标志。CBCT获得图像与定位CT图像配准得到左右(X)、上下(Y)、前后(Z)方向的平移误差和绕前后(R)方向的旋转误差,ETX拍摄获得双斜位片,与计划DRR配准后得到平移误差和旋转误差,记录两种验证方式的移位误差值,对CBCT及ETX验证进行组间配对t检验。结果分次间CBCT扫描在X、Y、Z、R方向的平均移位误差分别为(0.38±0.26)cm,(0.49±0.37)cm,(0.32±0.19)cm,(0.85±0.60)cm。分次内在X与Y方向,ETX_180较ETX_0平均移位误差分别增加21.7%与19.2%,且差异有统计学意义(P<0.05),在Z与R方向,ETX验证间差异无统计学意义(P>0.05)。结论NSCLC-SBRT分次间行CBCT图像引导能明显减少摆位误差,分次内行ETX拍片验证能有效监测单个治疗过程中的移位误差,提高治疗精度。

Application of Variance Component Analysis (ANOVA) in Setup Errors and PTV Margins for Lung Cancer with Stereotactic Body Radiation Therapy (SBRT)

Purpose: To investigate the feasibility of applying ANOVA newly proposed by Yukinori to verify the setup errors, PTV (Planning Target Volume) margins, DVH for lung cancer with SBRT. Methods: 20 patients receiving SBRT to 50 Gy in 5 fractions with a Varian iX linear acceleration were selected. Each patient was scanned with kV-CBCT before the daily treatment to verify the setup position. Two other error calculation methods raised by Van Herk and Remeijer were also compared to discover the statistical difference in systematic errors (Σ), random errors (σ), PTV margins and DVH. Results: Utilizing two PTV margin calculation formulas (Stroom, Van Herk), PTV calculated by Yukinori method in three directions were (5.89 and 3.95), (5.54 and 3.55), (3.24 and 0.78) mm;Van Herk method were (6.10 and 4.25), (5.73 and 3.83), (3.51 and 1.13) mm;Remeijer method were (6.39 and 4.57), (5.98 and 4.10), (3.69 and 1.33) mm. The volumes of PTV using Yukinori method were significantly smaller (P < 0.05) than Van Herk method and Remeijer method. However, dosimetric indices of PTV (D98, D50, D2) and for OARs (Mean Dose, V20, V5) had no significant difference (P > 0.05) among three methods. Conclusions: In lung SBRT treatment, due to fraction reduction and high level of dose per fraction, ANOVA was able to offset the effect of random factors in systematic errors, reducing the PTV margins and volumes. However, no distinct dose distribution improvement was founded in target volume and organs at risk.

Considerations and Experience in the Treatment of Lung Cancer with VMAT SBRT + DIBH in Arms-Down Position

The arms-up position is the most common treatment position adopted for lung cancer patients treated with radiation therapy. However, many elderly or frail patients have shoulder problems and cannot tolerate such an overstretched position for an extended period. Therefore, the arms-down position becomes the only alternative for this group of patients during radiation therapy. Even though the arms-down position is not ideal, it does provide a stable and comfortable patient immobilization position for radiation treatments that require a longer delivery time, such as stereotactic body radiation therapy (SBRT). In this study, we designed a protocol to treat lung cancer patients with VMAT stereotactic body radiation therapy (VMAT SBRT) and deep inspiration breath-hold (DIBH) in the arms-down position. Our initial clinical experience with this protocol indicates that it is reliable for patient immobilization and accurate in delivered dosimetry.

分析TPS-ZOOM功能在肺肿瘤SBRT靶区体积勾画中的差异

目的:探索TPS(放射治疗计划系统)-ZOOM(缩放)功能在肺肿瘤立体定向体部放射治疗(stereotactic body radiation therapy,SBRT)靶区体积勾画中的临床差异。方法:临床分析25个肺内拟行SBRT治疗的可见病灶;其中17个病灶≤3 cm,3 cm <8个病灶≤5 cm。同一个放疗医师分别在TPS-ZOOM取值为100%、150%、200%、250%、300%、400%、500%、600%、700%、800%等10组缩放图像上分别勾画GTVx=(1,1. 5,2,2. 5,3,4,5,6,7,8)每组25个GTV共计250个病灶数据信息。采用SPSS 20. 0对每一个病灶均采用Spearman行相关性分析; ANOVA方差分析检验1 0组间的勾画差异,P <0. 05为统计学有差异。结果:92%(23/25)病灶体积与缩放值大小呈负相关; 1 0组数据总体比较F=0. 178,P=0. 916,无统计学差异;分层分析≤3 cm组和> 3~5 cm组F分别为0. 176和0. 272,P值分别为0. 900和0. 980,均未见统计学差异。结论:对小于5 cm的肺部病灶,各病灶缩放值与靶区体积呈一定负相关,但总体各缩放值体积数据间未见统计学差异;因拟行SBRT的病灶体积较小,为了便于临床医师较易识别病灶边缘与勾画靶区,建议缩放150%~200%。

Acuros-Based Planning with Density Override for Lung SBRT by a Dynamic Conformal Arc Technique: Comparative Evaluation with AAA-Based Planning in Four-Dimensional Dose

The purpose of this study was to evaluate a planning strategy based on Acuros with density override in comparison with AAA without and with the override. Ten lung-tumor patients were selected with each PTV size around 2 - 4 cm and were imaged using slow scan, followed by four-dimensional (4D) imaging limited to the target. On each phase-specific image, gross tumor volume (GTV) was contoured. Summed over all phases, an integrated GTV (iGTV) was generated and copied to the slow scan. A treatment plan was created using a dynamic-conformal-arc technique with AAA to prescribe 60 Gy to 95% of PTV (iGTV + 0.5 cm). Each AAA-based plan was regenerated by overriding the density of the setup margin of PTV by GTV density (modeling tumor-position uncertainty). It was also regenerated with Acuros and the override. The three plans were validated in 4D dose to PTV, after similarly overriding PTV density (phase-specific), accurately calculating with Acuros, and summing the phase-specific plans through organ/dose registration. The Acuros-based plan with the override, the AAA-based plan, and the AAA-based plan with the override provided 4D PTV doses of 63.9, 67.9, and 62 Gy at D95%, respectively, averaged over all patients. The override with Acuros and AAA produced lesser 4D doses, closer to the associated 3D doses, respectively, than that without the override, with better conformity and inhomogeneity. With the override in common, Acuros provided a greater dose to PTV than that by AAA. The Acuros with the override, which was more accurate than the AAA without the override, is clinically recommended.

Lung SBRT through Radiobiology

Purpose: Stereotactic body radiation therapy (SBRT) has emerged as a standard treatment modality for medically inoperable early-stage lung cancer patients. The aim of this paper is to calculate radiobiological parameters for a sample of 39 patients who underwent lung SBRT. Materials and Methods: For SBRT, a typical regimen of 50 Gy in 4 - 5 fractions results in local tumor control rates around 99.9%. We calculate dose volume histograms (DVHs) of targeted tumors and organs at risk for 39 patients. All patients received 4D imaging, and their internal treatment volumes (ITVs) were created by phase-based sorting of multiple CT datasets. Planning target volume (PTV) diameters ranged from 2.0 to 5.7 cm. The DVHs for the PTV and organs at risk were analyzed using a Biosuite algorithm to calculate the equivalent uniform dose (EUD), tumor control probability (TCP) via a Poisson model, and normal tissue complication probability (NTCP) via an LKB model. The radiobiological effects were analyzed by correlating EUD and TCP with PTV volumes. Results: The mean PTV volume was 31.60 ± 25.55 cc. The mean EUDs were 5.19 ± 2.84, 5.66 ± 4.95, 61.45 ± 29.18, 3.31 ± 5.92, 6.45 ± 5.18, and 12.22 ± 5.94 Gy for lungs, spinal cord, chest/ribs, heart, esophagus, and skin, respectively. On average, the heart had the lowest EUD and the chest/ribs had the highest (61.45 ± 29.18 Gy). The mean NTCPs were estimated at 3.75% ± 2.61%, 36.25% ± 36.42%, and 0.59% ± 1.48%, for the lungs, chest and esophagus, respectively. The NTCPs of spinal cord, heart, and skin were 0.00%. The mean TCP value was 99.72% ± 0.44%. The mean BED value for our study was 109.49 Gy. Conclusions: We have calculated radiobiological predictors based on DVHs for early-stage non-small cell lung cancer via SBRT. Our calculated predictors are compatible with previously published SBRT reports.