The influence of patient geometry on the selection of chest wall irradiation techniques in post-mastectomy breast cancer patients.

BACKGROUND AND PURPOSE: To evaluate three chest wall (CW) irradiation techniques: wide tangential photon beams, direct appositional electron field and electron arc therapy with regards to target coverage and normal tissue tolerance. MATERIALS AND METHODS: Thirty-two post-mastectomy breast cancer patients were planned using three CW irradiation techniques. Computed tomography (CT) simulation was done on all patients and clinical target, heart and lung volumes were contoured. For each technique, dose distributions and dose-volume histograms (DVH) were calculated. Pass/fail criteria were applied based on volumetric target and critical structure dose coverage. Passing criteria for target was 95% of target receiving 95% of dose using a standard dose of 50 Gy/25 fractions, for heart 相似文献   

Electron arc therapy: physical measurement and treatment planning techniques

An electron beam arc therapy technique has been developed for the treatment of the post-mastectomy chest wall using a clinical linear accelerator modified for arc therapy. The effects on the dose distribution of primary X ray collimators, secondary cerrobend blocks attached to the accelerator accessory tray, and tertiary cerrobend casting of the treatment area on the patient's thorax have been investigated. Multiple electron energies within the same arc, variable rad per degree, and variable shaped secondary and tertiary applicators have been employed to optimize dose uniformity across the treated surface. A computerized treatment planning program has been developed to aid in visualization and optimization of dose distributions. A simple technique to estimate the width variation in the secondary collimator necessary to compensate for radial patient thickness changes in the cephalocaudad direction is described. Electron beam energies of 6 MeV, 9 MeV, 12 MeV, 15 MeV, and 18 MeV have been studied. The physical measurements needed to implement this technique are described, and a comparison of electron arc therapy dose distributions with other standard treatment techniques is presented.     

Postmastectomy electron beam chest wall irradiation in women with breast cancer: a clinical step toward conformal electron therapy

PURPOSE: Electron beam radiotherapy of the chest wall with or without lymph node irradiation has been used at the Institut Curie for >20 years. The purpose of this report was to show the latest improvements of our technique developed to avoid hot spots and improve the homogeneity. METHODS AND MATERIALS: The study was split into two parts. A new electron irradiation technique was designed and compared with the standard one (dosimetric study). The dose distributions were calculated using our treatment planning software ISIS (Technologie Diffusion). The dose calculation was performed using the same calculation parameters for the new and standard techniques. Next, the early skin toxicity of our new technique was evaluated prospectively in the first 25 patients using Radiation Therapy Oncology Group criteria (clinical study). RESULTS: The maximal dose found on the five slices was 53.4 +/- 1.1 Gy for the new technique and 59.1 +/- 2.3 Gy for the standard technique. The hot spots of the standard technique plans were situated at the overlap between the internal mammary chain and chest wall fields. The use of one unique field that included both chest wall and internal mammary chain volumes solved the problem of junction. To date, 25 patients have been treated with the new technique. Of these patients, 12% developed Grade 0, 48% Grade 1, 32% Grade 2, and 8% Grade 3 toxicity. CONCLUSIONS: This report describes an improvement in the standard postmastectomy electron beam technique of the chest wall. This new technique provides improved target homogeneity and conformality compared with the standard technique. This treatment was well tolerated, with a low rate of early toxicity events.     

Effects of a sonographic technique for determining chest wall thickness in treatment planning for breast carcinoma

This study investigated the use of a sonographic technique of determining chest wall thickness and the impact of dosimetric correction for lung inhomogeneity on treatment planning for breast irradiation after lumpectomy or partial mastectomy. The thickness of the chest wall in three planes of the radiation field was obtained using a B-mode ultrasound scanner and the location of the pleura-lung interface was marked on the contour of the chest wall in each plane. Treatment plans for 88 patients were developed with and without correction for the lung tissue included in the radiation volume. All patients were irradiated with an opposing pair of tangential fields to the breast with a 6 MV X ray beam using an isocentric set-up. Within the treatment volume, dose variation of +/- 5% of the prescribed tumor dose was aimed for in the treatment planning. With correction for lung tissue, the proportion of treatments given with a wedge filter was found to be on the average 20% less than it would be without lung correction. The described sonographic technique is simple to perform and reproducible. It improves the accuracy of dosimetry in treatment planning for breast carcinoma.     

Electron arc therapy: Clinical experience with chest and irradiation

In order to overcome the technical problems commonly encountered in fixed field photon and electron beam chest wall irradiation, we have treated the chest wall in 22 breast cancer patients with a moving electron beam that rotates about the patient's thorax. This paper discusses the clinical results of chest wall treatment by electron arc therapy. Twenty-one patients were treated following mastectomy, 16 electively because of high risk for local failure, and 5 because of local recurrence. One patient with advanced local-regional disease was treated primarily. During a median follow-up period of 24 months there has been one chest failure in one of the patients treated for local recurrence. No major complications were observed in skin, lung, soft tissue or esophagus, even in the 7 patients recently or concomitantly treated with multiagent cytotoxic chemotherapy. In 3 patients, small areas of telangiectasia developed in the region of abutment of the electron arc field to a photon field used to irradiate the supraclavicular nodal area. We conclude that the technique as applied to these patients is safe and efficacious. In certain clinical settings it has advantage over standard, fixed field approaches to treat the chest wall.     

A multidisciplinary approach to improving the quality of tangential chest wall and breast irradiation for carcinoma of the breast.

Physicists, radiotherapists and radiographers have worked together to enhance the quality and accuracy of radiotherapy for tangential irradiation of the chest wall and breast. Each stage of the process has been reassessed and improved. A technique has been developed on the treatment simulator which determines the required beam directions and sizes in a straightforward manner. A computerised tomography facility has also been developed on the simulator and this provides one or more slices for planning through the treatment volume, thus allowing accurate determination of external contour and lung position with the patient in the treatment position. The beam edge entry points and the isocentre position can be seen from radiation opaque markers placed on the skin surface, allowing accurate reproduction of the treatment beam positions as set on the simulator. A photon beam algorithm that corrects for the changes in scatter dose in a 3-dimensional (3-D) inhomogeneous situation has been developed and applied to tangential chest wall irradiation. This has shown large differences (up to 10%) in dose compared to a conventional 2-dimensional algorithm. The changes in dose distribution due to the accurate determination of lung position have also been investigated. A method has been developed of measuring the volume of ipsilateral lung irradiated. Dose-area histograms are used to evaluate the fraction of the lung area irradiated in the central slice, and an estimate of the volume irradiated can be made using a beam's eye radiograph and the simulator CT image.     

乳腺癌根治术后胸壁电子束旋转照射的临床应用

放射治疗是高危乳腺癌根治术后综合治疗的重要组成部分。胸壁和锁骨上区是最重要的术后辅助放疗部位。目前有多种胸壁照射方式,由于胸廓特殊的几何形状,传统的照射方法难以达到合理的剂量分布。电子束旋转照射技术利用电子束的剂量分布特点,根据胸壁的形状和靶区的深度选择不同的能量,能使靶区达到理想的剂量分布,同时降低心、肺晚期放射损伤,在胸壁照射中具有较大的优势及其较高的临床应用价值。本文就乳腺癌根治术后胸壁电子束旋转照射的临床应用作一综述。     

Electron arc irradiation of the postmastectomy chest wall with CT treatment planning: 20-year experience.

PURPOSE: Since 1980, electron arc irradiation of the postmastectomy chest wall has been the preferred radiotherapy technique at the University of Utah for patients with advanced breast cancer. We report the results of this technique in 156 consecutive Stage IIA-IIIB patients treated from 1980 to 1998. METHODS: CT treatment planning was used in all patients to identify chest wall thickness and internal mammary lymph node depth. Computerized dosimetry was used to deliver total doses of 50 Gy in 5-1/2 weeks to the chest wall and the internal mammary lymph nodes with electron arc therapy. Patients were assessed for local, regional, and distant control of disease and for survival. Univariate and multivariate proportional hazards were modeled using a hierarchical nonproportional semiparametric model testing the following prognostic factors: age, stage, tumor size, number of positive lymph nodes, estrogen receptor status, and dose. End points evaluated included disease-free survival, cause-specific survival, and overall survival. RESULTS: Eighty-one percent of patients were at high risk for local-regional failure because of > T2 primary tumor or > 3 positive axillary lymph nodes. The median number of positive lymph nodes was 5, and the median tumor size was 3.5 cm. Actuarial 10-year local-regional control and overall survival were 95% and 52%, respectively. In multivariate analysis, the only factor prognostic for disease-free survival, cause-specific survival, and overall survival was the number of positive lymph nodes (p < 0.001). The 10-year rates of local-regional control for patients with 0, 1-3, 4-9, and > or = 10 involved lymph nodes were 100%, 98%, 93%, and 89%, respectively. The only rates of acute and chronic radiotherapy toxicity > or = 2 by RTOG/EORTC criteria were skin related and observed in 44% and 10% for acute and late reactions, respectively. CONCLUSION: These data demonstrate excellent local-regional control rates with electron arc therapy of the postmastectomy chest wall in patients with advanced breast cancer. Our 20-year experience with electron arc radiotherapy has demonstrated the safety and efficacy of this technique. The advantage of this technique is that the internal mammary lymph node chain can be easily encompassed while the dose to heart and lung is minimized; it also obviates match lines in areas of high risk.     

乳腺癌术后胸壁电子线放射治疗单野与分野计划比较

目的：乳腺癌术后胸壁电子线放射治疗时单野与分野治疗对整个胸壁照射区剂量分布比较。方法：对乳腺癌根治术后病人进行模拟CT定位,用Varian的Eclipse治疗计划系统进行CT图像重建、靶区勾画。6MeV或9MeV电子线对所勾画的靶区进行单野和分野计划设计,计算并比较整个靶区的剂量分布。结果：乳腺癌术后胸壁照射由单野改成二野照射后,80％剂量曲线所包靶区体积由47％上升到84％,90％剂量曲线所包靶区体积由28％上升到72％。结论：进行乳腺癌根治术后大胸壁电子线照射时,单野照射剂量分布不均且靠近内乳区和腋中线区剂量严重不足,若在病人体表弯曲处进行分野,分野后进行二野照射则大大提高内乳区和腋中线区的剂量,提高了整个靶区的剂量,从而满足临床剂量要求。     

Beam intensity modulation for penumbra enhancement and field length reduction in lung cancer treatments: a dosimetric study.

BACKGROUND AND PURPOSE: In a recent treatment planning study, a previously published technique for superior-inferior field length reduction for prostate cancer patients, based on penumbra enhancement using static beam intensity modulation (BIM) with a multileaf collimator, was investigated for lung cancer treatments. For the patient group studied, the field lengths could be reduced by 1.4 cm and an average dose escalation of 6 Gy (maximum 16 Gy) appeared to be possible without any increase in the calculated risk of radiation pneumonitis. However, this planning study was performed with a treatment planning system that does not correctly account for the increased lateral secondary electron transport in lung tissue, resulting in too steep beam penumbrae. Therefore, prior to clinical implementation, an extensive dosimetric study was performed to evaluate and optimize BIM for penumbra enhancement and superior-inferior field length reduction in lung cancer treatments. MATERIALS AND METHODS: Film dosimetry was performed in several phantoms consisting of water equivalent and lung equivalent materials, both for a 6 and a 10 MV photon beam. Measured dose distributions were used to (i) adapt the BIM technique to properly account for increased lateral secondary electron transport, (ii) compare BIM dose distributions in lung material with dose distributions of standard treatment fields, and (iii) investigate the use of our treatment planning system for the design of BIM plans for lung cancer patients. RESULTS: Compared with our treatment planning study the superior and inferior boost fields, used in the BIM technique for penumbra enhancement, had to be longer and of a higher weight to compensate for the increased lateral secondary electron transport in lung tissue. With these modifications in the BIM technique, field lengths could indeed be reduced by 1.4 cm compared with treatment with standard fields, without the appearance of underdosages in the most superior and inferior target areas, whilst better sparing the healthy lung tissue. Practical rules were derived to use our treatment planning system for the design of BIM treatment plans. CONCLUSIONS: In spite of the increased lateral secondary electron transport in lung tissue, static BIM with a multileaf collimator may effectively be used for penumbra enhancement and superior-inferior field length reduction in lung cancer treatments.     

Electron arc therapy: chest wall irradiation of breast cancer patients

From 1980 to October 1985 we treated 45 breast cancer patients with electron arc therapy. This technique was used in situations where optimal treatment with fixed photon or electron beams was technically difficult: long scars, recurrent tumor extending across midline or to the posterior thorax, or marked variation in depth of target tissue. Forty-four patients were treated following mastectomy: 35 electively because of high risk of local failure, and 9 following local recurrence. One patient with advanced local regional disease was treated primarily. The target volume boundaries on the chest wall were defined by a foam lined cerrobend cast which rested on the patient during treatment, functioning as a tertiary collimator. A variable width secondary collimator was used to account for changes in the radius of the thorax from superior to inferior border. All patients had computerized tomography performed to determine Internal Mammary Chain depth and chest wall thickness. Electron energies were selected based on these thicknesses and often variable energies over different segments of the arc were used. The chest wall and regional node areas were irradiated to 45 Gy-50 Gy in 5-6 weeks by this technique. The supraclavicular and upper axillary nodes were treated by a direct anterior photon field abutted to the superior edge of the electron arc field. Follow-up is from 10-73 months with a median of 50 months. No major complications were observed. Acute and late effects and local control are comparable to standard chest wall irradiation. The disadvantages of this technique are that the preparation of the tertiary field defining cast and CT treatment planning are labor intensive and expensive. The advantage is that for specific clinical situations large areas of chest wall with marked topographical variation can be optimally, homogeneously irradiated while sparing normal uninvolved tissues.     

Multivariate analysis of pulmonary fibrosis after electron beam irradiation for postmastectomy chest wall and regional lymphatics: evidence for non-dosimetric factors.

BACKGROUND AND PURPOSE: To evaluate the factors associated with pulmonary fibrosis after postmastectomy electron beam irradiation of chest wall and regional lymphatics in patients with breast cancer. MATERIALS AND METHODS: From July 1987 through July 1994, 109 women with stage II and III breast cancer receiving modified radical mastectomies were managed by postoperative electron beam irradiation. Doses of 46 to 50.4 Gy were delivered to the chest wall covered with bolus, internal mammary nodes, supraclavicular nodes and axillary lymph nodes via 12 or 15 MeV single portal electron beam. Seventeen patients received additional 10-16 Gy surgical scar boost via 9 MeV electron beam. Comparison of pre-treatment and post-treatment chest X-ray films were used to monitor the development of pulmonary fibrosis. RESULTS: Only Grade 1 radiation-induced late pulmonary toxicity was noted in 33 patients (29%). Twenty-six patients (24%) developed pulmonary fibrosis under unbolused chest wall. Lung fibrosis under bolused chest wall was noted in 11 patients (10%). Statistical difference (P<0.01) was noted between the incidence of fibrosis in these two sites. In multivariate analysis of lung fibrosis under unbolus-covered chest wall, the independent prognostic factors are low body mass index (BMI) (P<0.01), tamoxifen taking (P=0.03), and no treatment interruption (P=0.03). No independent factor was associated with lung fibrosis under bolus-covered chest wall in multivariate analysis. CONCLUSIONS: In the analysis of pulmonary fibrosis induced by unbolused electron beam, BMI rather than body weight and body height is a strong prognostic factor. Tamoxifen and short overall time can predispose the development of lung fibrosis.     

乳腺癌术后胸壁电子线放射治疗单野与分野计划比较

目的:乳腺癌术后胸壁电子线放射治疗时单野与分野治疗对整个胸壁照射区剂量分布比较。方法:对乳腺癌根治术后病人进行模拟CT定位,用Varian的Eclipse治疗计划系统进行CT图像重建、靶区勾画。6MeV或9MeV电子线对所勾画的靶区进行单野和分野计划设计,计算并比较整个靶区的剂量分布。结果:乳腺癌术后胸壁照射由单野改成二野照射后,80%剂量曲线所包靶区体积由47%上升到84%,90%剂量曲线所包靶区体积由28%上升到72%。结论:进行乳腺癌根治术后大胸壁电子线照射时,单野照射剂量分布不均且靠近内乳区和腋中线区剂量严重不足,若在病人体表弯曲处进行分野,分野后进行二野照射则大大提高内乳区和腋中线区的剂量,提高了整个靶区的剂量,从而满足临床剂量要求。     

Chest wall irradiation with MLC-shaped photon and electron fields

PURPOSE: To improve the treatment technique for chest wall irradiation, using the multileaf collimator (MLC) of the MM50 Racetrack Microtron to shape both photon and electron beams, and to check the dose delivery in the match-line region of these fields for the routine and improved technique. METHODS AND MATERIALS: Using diode and film phantom measurements, the optimal number of photon beam segments and their positions relative to the electron beam were determined. On phantoms, and during actual patient treatment using in vivo dosimetry, the dose homogeneity in the match-line region was determined for both the routine and improved techniques. RESULTS: Three photon beam segments (9-mm gap, perfect match, and 9-mm overlap) were used to match the electron beam, resulting in minimum-maximum dose values in the match-line region of 88-109%, compared to 80-115% for the routine technique (2 photon beam segments). During patient treatment, the average minimum and maximum dose values were 95% and 115%, respectively, compared to 78% and 127%, respectively, for the routine technique. The interfraction variation in dose delivery was reduced from 11.0% (1 SD) to 4.6% (1 SD). The actual treatment time was reduced from 10 to 4.5 min. CONCLUSION: Using the MLC of the MM50 to shape both photon and electron beams, an improved treatment technique for chest wall irradiation was developed, which is less labor intensive, faster, and yields a more homogeneous, and better reproducible dose delivery.     

乳腺癌改良根治术后三种放疗技术的剂量学对比研究

目的 分析比较容积调强弧形治疗(VMAT)与固定野调强放疗(F_IMRT)、电子束联合VMAT (E&VMAT)技术在乳腺癌改良根治术后放疗中的剂量学差异,为临床选择治疗方案提供参考。方法 随机选择乳腺癌改良根治术后放疗的左乳腺癌患者 10例,靶区包括患侧胸壁和锁骨上淋巴引流区,处方剂量43.5Gy (2.9 Gy/次)。基于Pinnacle³计划系统为每位患者分别设计VMAT、F_IMRT、E&VMAT (胸壁靶区部分电子束照射、锁骨上区部分VMAT照射)计划。对比评价靶区剂量分布适形度与均匀性、危及器官受量以及治疗实施时间。结果 VMAT计划能改善靶区剂量分布,靶区剂量适形指数和均匀性指数均优于F_IMRT和E&VMAT计划(均 P<0.05)。VMAT计划患侧肺平均剂量 、V30Gy、V20Gy、V10Gy均优于F_IMRT和E&VMAT计划(均 P<0.05)。VMAT计划患侧 肺V5Gy优于F_IMRT计划(P<0.05),与E&VMAT计划 的V5Gy相近(P>0.05)。VMAT计划的心脏、健侧乳腺、健侧肺均能满足临床剂量限制要求。VMAT、F_IMRT、E&VMAT计划的治疗时间分别为(326±27)、(1082±169)、(562±48) s。结论 与F_IMRT和E&VMAT计划相比,VMAT计划质量更优,治疗时间更短,具有较高的临床应用价值。     

乳腺癌改良根治术后CT模拟胸壁电子线照射的剂量学探讨

目的评价乳腺癌改良根治术后CT模拟定位下胸壁电子线照射的靶区和心肺受照体积和剂量分布情况。方法20例有胸壁照射适应证的乳腺癌改良根治术后患者,行CT模拟定位,三维治疗计划系统将CT图像进行数字化重建,勾画胸壁CTV及心、肺等危及器官,并计算胸壁及其心、肺受照体积和受照剂量。胸壁处方剂量为5000cGy。结果左侧乳腺癌靶区的Dmax为(5536±301)cGy、Dmean为(4823±129)cGy、D90为(4543±290)cGy,同侧肺Dmean为(1724±624)cGy、V20为(36±13)%。心脏Dmean为(1008±457)cGy、V30为(13±9)%。右侧乳腺癌靶区的Dmax为(5554±253)cGy、Dmean为(4783±89)cGy、D90为(4496±101)cGy、同侧肺Dmean为(1416±567)cGy、V20为(30±12)%。结论通过CT模拟定位制定胸壁电子线照射放疗计划,能更准确地了解靶区和正常组织的剂量分布,从而能更好地优化放疗计划。     

电子线旋转治疗技术在乳腺癌术后胸壁照射中的应用

随着肿瘤综合治疗的不断发展,乳腺癌的治疗策略发生了很大变化。但放射治疗作为一种局部治疗方法在乳腺癌综合治疗中仍占重要地位。乳腺癌术后胸壁复发占所有局部复发的44％～69％,居第一位,成为乳腺癌术后放射治疗的最重要靶区。然而,由于胸廓特殊的几何形状,传统的照射方法难以达到合理的剂量分布。电子线旋转治疗技术利用电子线的剂量分布特点、结合胸壁的形状和靶区的深度选择不同的能量,使靶区达到合理的剂量分布,同时降低心、肺受量,在胸壁照射中具有较大的优势。临床实践也证实,电子线旋转照射与常规照射技术相比具有局部控制率高、心肺毒性小、皮肤反应轻等优点,在胸壁照射中具有较高的临床应用价值。     

Radiotherapy of the breast and chest wall: treatment volume]

The radiotherapy of the breast or the chest wall is a complex technique. The definition of the gross tumour volume and the clinical target volume depends on clinical, anatomical and histological criteria. The volumes are located by physical examination, mammography, echography and tomodensitometry. The implantation of surgical clips in the lumpectomy cavity is useful for the boost field. The planning target volume takes into consideration movements of tissues during respiration and variations in beam geometry characteristics. The organs at risk (heart, lung) must be considered systematically. Technical contrivances are necessary to modify and homogenize dose distribution. Conformational irradiation allows an individually design treatment planning. Intensity-modulated radiotherapy technique is a future advantageous technique still under evaluation.     

Advances in treatment techniques: arc-based and other intensity modulated therapies

Treatment planning and radiation delivery techniques have advanced significantly during the past 2 decades. The development of the multileaf collimator has changed the scope of radiotherapy. The dynamic conformal arc technique emerged from traditional cone-based conformal arc therapies, which aim to improve target dose uniformity and reduce normal tissue doses. With dynamic conformal arc, the multileaf collimator aperture is shaped dynamically to conform to the target. With the advent of intensity-modulated radiotherapy (IMRT), the concept of arc therapy in combination with IMRT has enabled better-quality dose distributions and more efficient delivery. Helical tomotherapy has been developed to treat targets sequentially by modulating the beam intensity in each "slice" of the patient. Helical tomotherapy offers improved dose distributions for complicated treatments, such as whole-body radiation. Intensity-modulated arc therapy has been studied to modulate fluences in a cone beam rather than fan beam geometry to improve delivery efficiency. This article reviews arc-based IMRT, intensity-modulated arc therapy, and helical tomotherapy techniques. We compare the dosimetric results reported in the literature for each technique in various treatment sites. We also review the application of these techniques in specialized clinical procedures including total marrow irradiation, simultaneous treatment of multiple brain metastases, dose painting, simultaneous integrated boost, and stereotactic radiosurgery.