Reduction of cardiac and lung complication probabilities after breast irradiation using conformal radiotherapy with or without intensity modulation.

PURPOSE: The main purpose of this work is to reduce the cardiac and lung dose by applying conformal tangential beam irradiation of the intact left breast with and without intensity modulation, instead of rectangular tangential treatment fields. The extension of the applicability of the maximum heart distance (MHD) to conformal tangential fields as a simple patient selection criterion, identifying patients for which rectangular and conformal tangential fields without intensity modulation will result in unacceptable normal tissue complication probability (NTCP) values for late cardiac mortality (e.g. >2%), was also investigated. MATERIALS AND METHODS: Three-dimensional treatment planning was performed for 17 left-sided breast cancer patients. Three different tangential beam techniques were compared: (1) optimized wedges without blocks, (2) optimized wedges with conformal blocks and (3) intensity modulation. Plans were evaluated using dose-volume histograms (DVHs) for the planning target volume (PTV), the heart and the lungs. NTCPs for radiation pneumonitis and late cardiac mortality were calculated using the DVH data. The MHD was measured for all rectangular (MHD(rectangular)) and conformal (MHD(conformal)) treatment plans. RESULTS: For all patients, on average, part of the PTV receiving a dose between 95 and 107% of the prescribed dose of 50Gy in 25 fractions of 2Gy was 90.8% (standard deviation (SD): 5.0%), 92.8% (SD: 3.5%) and 92.8% (SD: 3.6%) for the intensity modulation radiation therapy (IMRT), conformal and rectangular field treatment techniques, respectively. The NTCP for radiation pneumonitis was 0.3% (SD: 0.1%), 0.4% (SD: 0.4%) and 0.5% (SD: 0.6%) for the IMRT, conformal and rectangular field techniques, respectively. The NTCP for late cardiac mortality was 5.9% (SD: 2.2%) for the rectangular field technique. This value was reduced to 4.0% (SD: 2.3%) with the conformal technique. A further reduction to 2.0% (SD: 1.1%) could be accomplished with the IMRT technique. The NTCP for late cardiac mortality could be described as a second order polynomial function of the MHD. This function could be described with a high accuracy and was independent of the technique for which the MHD was determined (r(2)=0.88). In order to achieve a NTCP value for late cardiac mortality below 1, 2 or 3%, the MHD should be equal to or smaller than 11, 17 or 23 mm, respectively. If such a maximum complication probability cannot be accomplished, a treatment using the IMRT technique should be considered. CONCLUSIONS: The use of conformal tangential fields decreases the NTCP for late cardiac toxicity on average by 30% compared to using rectangular fields, while the tangential IMRT technique can further reduce this value by an additional 50%. The MHD can be used to estimate the NTCP for late cardiac mortality if rectangular or conformal tangential treatment fields are used.     

Cardiac and pulmonary doses and complication probabilities in standard and conformal tangential irradiation in conservative management of breast cancer.

BACKGROUND AND PURPOSE: The clinical benefit of irradiating the intact breast after lumpectomy must be weighted against the risk of severe toxicity. We present a study on cardiac and pulmonary dose-volume data and the related complication probabilities of tangential breast irradiation having the following objectives: (1) to quantify the sparing of the organs at risk (ORs), the heart and the lung, achieved by three-dimensional (3-D) conformal tangential irradiation (CTI) as compared to standard tangential irradiation (STI); (2) to elucidate the uncertainty in radiation tolerance data; and (3) to analyse the relation between the amount of OR irradiated and the resulting morbidity risk. MATERIAL AND METHODS: Computed tomography (CT)-based 3-D treatment plans of 26 patients prescribed to CTI of the intact breast were applied. Contour-based STI has been our routine treatment, and was reconstructed for all patients. Dose-volume data and normal tissue complication probability (NTCP) predictions from the probit and relative seriality models with several cardiac and pulmonary tolerance parameterizations were analysed and compared. RESULTS AND CONCLUSIONS: A significant amount of normal tissues can be spared from radiation by using CT-based CTI, resulting in a 50% reduction of the average excess cardiac mortality risk in the left-sided cases. The risks for pericarditis and pneumonitis were too low to reveal any clinically significant difference between the treatments. For the STI set-up, a regression analysis showed that the excess cardiac mortality risk increased when larger parts of the heart were inside the fields. However, the different excess cardiac mortality and pneumonitis tolerance parameters resulted in statistically significant different NTCPs, which precluded the ability to accurately predict absolute NTCPs after tangential breast irradiation. Despite this uncertainty the different series of cardiac and pulmonary risk predictions were in relatively good agreement when small volumes of the ORs were irradiated. From the present data and without consideration of patient or organ motion, it therefore appears that tangential breast irradiation with less than 1 cm of the heart and 2-2.5 cm of the lung included inside the treatment fields will cause at most 1 per thousand risk for cardiac mortality and pulmonary morbidity. CT-based CTI should be considered, in particular for the left-sided cases, if these requirements cannot be met.     

Breast-conserving radiation therapy using combined electron and intensity-modulated radiotherapy technique.

BACKGROUND AND PURPOSE: To explore the feasibility of a multi-modality breast-conserving radiation therapy treatment technique to reduce high dose to the ipsilateral lung and the heart when compared with the conventional treatment technique using two tangential fields. MATERIALS AND METHODS: An electron beam with appropriate energy was combined with four intensity modulated photon beams. The direction of the electron beam was chosen to be tilted 10-20 degrees laterally from the anteroposterior direction. Two of the intensity-modulated photon beams had the same gantry angles as the conventional tangential fields, whereas the other two beams were rotated 15-25 degrees toward the anteroposterior directions from the first two photon beams. An iterative algorithm was developed which optimizes the weight of the electron beam as well as the fluence profiles of the photon beams for a given patient. Two breast cancer patients with early-stage breast tumors were planned with the new technique and the results were compared with those from 3D planning using tangential fields as well as 9-field intensity-modulated radiotherapy (IMRT) techniques. RESULTS: The combined electron and IMRT plans showed better dose conformity to the target with significantly reduced dose to the ipsilateral lung and, in the case of the left-breast patient, reduced dose to the heart, than the tangential field plans. In both the right-sided and left-sided breast plans, the dose to other normal structures was similar to that from conventional plans and was much smaller than that from the 9-field IMRT plans. The optimized electron beam provided between 70 to 80% of the prescribed dose at the depth of maximum dose of the electron beam. CONCLUSIONS: The combined electron and IMRT technique showed improvement over the conventional treatment technique using tangential fields with reduced dose to the ipsilateral lung and the heart. The customized beam directions of the four IMRT fields also kept the dose to other critical structures to a minimum.     

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。     

Cardiac and lung complication probabilities after breast cancer irradiation.

PURPOSE: To assess for locoregional irradiation of breast cancer patients, the dependence of cardiac (cardiac mortality) and lung (radiation pneumonitis) complications on treatment technique and individual patient anatomy. MATERIALS AND METHODS: Three-dimensional treatment planning was performed for 30 patients with left-sided breast cancer and various breast sizes. Two locoregional techniques (Techniques A and B) and a tangential field technique, including only the breast in the target volume, were planned and evaluated for each patient. In both locoregional techniques tangential photon fields were used to irradiate the breast. The internal mammary (IM)-medial supraclavicular (MS) lymph nodes were treated with an anterior mixed electron/photon field (Technique A) or with an obliquely incident mixed electron/photon IM field and an anterior electron/photon MS field (Technique B). The optimal IM and MS electron field dimensions and energies were chosen on the basis of the IM-MS lymph node target volume as delineated on CT-slices. The position of the tangential fields was adapted to match the IM-MS fields. Dose-volume histograms (DVHs) and normal tissue complication probabilities (NTCPs) for the heart and lung were compared for the three techniques. In the beam's eye view of the medial tangential fields the maximum distance of the heart contour to the posterior field border was measured; this value was scored as the Maximum Heart Distance. RESULTS: The lymph node target volume receiving more than 85% of the prescribed dose was on average 99% for both locoregional irradiation techniques. The breast PTV receiving more than 95% of the prescribed dose was generally smaller using Technique A (mean: 90%, range: 69-99%) than using Technique B (mean: 98%, range: 82-100%) or for the tangential field technique (mean: 98%, range: 91-100%). NTCP values for excess cardiac mortality due to acute myocardial ischemia varied considerably between patients, with minimum and maximum values of 0.1 and 7.5% (Technique A), 0.1 and 5.8% (Technique B) and 0.0 and 6.1% (tangential tech.). The NTCP values were on average significantly higher (P<0.001) by 1.7% (Technique A) and 1.0% (Technique B) when locoregional breast irradiation was given, compared with irradiation of the left breast only. The NTCP values for the tangential field technique could be estimated using the Maximum Heart Distance. NTCP values for radiation pneumonitis were very low for all techniques; between 0.0 and 1.0%. CONCLUSIONS: Technique B results in a good coverage of the breast and locoregional lymph nodes, while Technique A sometimes results in an underdosage of part of the target volume. Both techniques result in a higher probability of heart complications compared with tangential irradiation of the breast only. Irradiation toxicity for the lung is low in all techniques. The Maximum Heart Distance is a simple and useful parameter to estimate the NTCP values for cardiac mortality for tangential breast irradiation.     

放射生物模型在乳腺癌放疗计划评价中的比较

目的 比较分析不同放射生物模型的特性,以寻求评价乳腺癌放疗计划合理的放射生物模型.方法 比较预测放射性肺炎发生率和放射性心脏病死亡率的NTCP两种模型和TCP四种模型,计算相同DVH数据所得结果的差异;并分析同一模型中,输入DVH数据的形式、参数的选择等对结果的影响.结果 假设全肺平均照射30 Gy剂量时,NTCP-RSM模型预测的放射性肺炎发生率为32%,NTCP-Lyman模型预测的为54%.以发生放射性心脏病死亡率1%为例,NTCP-RSM模型对应的心脏平均照射剂量为28 Gy,而NTCP-Lyman模型对应的为40 Cy.应用LQ-Poisson-TCP模型、Poisson-TCP模型、Logit-TCP模型和Zaider-TCP模型,计算相同DVH数据库的平均TCP分别为21.1%、38.4%、41.0%和80.8%(P=0.000).采用不同栅格大小计算的NTCP/TCP结果差别较小.计算时采用物理剂量或LQED2剂量对NTCP/TCP结果有一定影响,采用物理剂量时的结果稍大.ft.和p值、肿瘤细胞密度、D50值和DVH简化方法对TCP的影响显著(P=0.000).结论 评价和优化乳腺癌放疗计划选择放射生物模型时,以NTCP-Lyman模型计算放射性肺炎和以NTCP-RSM模型计算放射性心脏病死亡率比较合理.TCP模型以LQ-Poisson-TCP模型比较符合临床实际.影响预测结果最大的是模型参数值的选取,选择时需要加以注意.这些模型目前有助于对不同治疗模式进行研究和比较,而不是给出对临床实际结果的精确预测.     

患者因素对乳腺癌保乳术后IMRT计划设计影响分析

目的 探讨患者VPTV、MHD、CLD、CTR对乳腺癌保乳术后IMRT计划设计的影响。方法 2016—2017年在我院接受全乳IMRT的48例女性乳腺癌保乳术后患者(左侧31例、右侧17例),放疗处方剂量为PTV 50 Gy,2 Gy/次。每个患者的调强计划同时使用物理参数和EUD对目标函数进行优化。采用一元和多元线性回归分析预测影响因子与OAR百分剂量体积、CI和HI间关系。结果 CTR和VPTV是左侧乳腺癌CI独立影响因素(R²值分别为0.56、0.56,P值分别为0.04、0)。CLD是左侧乳腺癌HI独立影响因素(R²=0.17,P=0.023),VPTV是右侧CI的独立影响因素(R²=0.48,P=0)。MHD和CTR是心脏VHeart30的预测因子。MHD和CLD是心脏DmaxHeart的预测因子。左侧乳腺癌预测公式为CI=0.38+0.32CTR,HI=1.06+0.02CLD。右侧CI=0.48。左侧Vlung20=12.68+3.18CLD,Vlung10=18.78+4.3CLD,Vlung5=26.2+5.2CLD,Dmeanlung=686.7+210.1CLD。心脏VHeart30=(-13.65)+30.5CTR+1.9MHD,DmaxHeart=5140.1+248.9MHD-195.6CLD。患者的心脏体积与MHD、VHeart10 、VHeart5、DmeanHeart和DmaxHeart无相关性。患者的全肺体积与CLD、Vlung20、Vlung10、Vlung5、Dmeanlung无相关性。左侧乳腺癌计划CI和HI的平均值分别为0.63±0.06(0.46~0.72)和1.09±0.02(1.074~1.14),右侧乳腺癌计划CI和HI的均值分别为0.65±0.08(0.48~0.76)和1.09±0.04(1.03~1.18)。结论 CTR、CLD和MHD可以预测左侧乳腺癌调强计划各个参数的合理性,右侧乳腺癌则不适用。据此生成的计算公式可以帮助物理师选择优选的射野设置方式,提高治疗计划的质量。     

Dosimetric and clinical advantages of deep inspiration breath-hold (DIBH) during radiotherapy of breast cancer

Background

To investigate the potential dosimetric and clinical benefits of Deep Inspiration Breath-Hold (DIBH) technique during radiotherapy of breast cancer compared with Free Breathing (FB).

Methods

Eight left-sided breast cancer patients underwent a supervised breath hold during treatment. For each patient, two CT scans were acquired with and without breath hold, and virtual simulation was performed for conventional tangential fields, utilizing 6 or 15 MV photon fields. The resulting dose–volume histograms were calculated, and the volumes of heart/lung irradiated to given doses were assessed. The left anterior descending coronary artery (LAD) mean and maximum doses were calculated, together with tumour control probability (TCP) and normal tissue complication probabilities (NTCP) for lung and heart.

Results

For all patients a reduction of at least 16% in lung mean dose and at least 20% in irradiated pulmonary volumes was observed when DIBH was applied. Heart and LAD maximum doses were decreased by more than 78% with DIBH. The NTCP values for pneumonitis and long term cardiac mortality were also reduced by about 11% with DIBH. The NTCP values for pericarditis were zero for both DIBH and FB.

Conclusion

Delivering radiation in DIBH conditions the dose to the surrounding normal structures could be reduced, in particular heart, LAD and lung, due to increased distance between target and heart, and to reduced lung density.

     

Intensity modulated versus non-intensity modulated radiotherapy in the treatment of the left breast and upper internal mammary lymph node chain: a comparative planning study.

BACKGROUND AND PURPOSE: To compare and evaluate intensity modulated (IMRT) and non-intensity modulated radiotherapy techniques in the treatment of the left breast and upper internal mammary lymph node chain. MATERIALS AND METHODS: The breast, upper internal mammary chain (IMC), heart and lungs were delineated on a computed tomography (CT)-scan for 12 patients. Three different treatment plans were created: (1) tangential photon fields with oblique IMC electron-photon fields with manually optimized beam weights and wedges, (2) wide split tangential photon fields with a heart block and computer optimized wedge angles, and (3) IMRT tangential photon fields. For the IMRT technique, an inverse planning program (KonRad) generated the intensity profiles and a clinical three-dimensional treatment planning system (U-MPlan) optimized the segment weights. U-MPlan calculated the dose distribution for all three techniques. The normal tissue complication probabilities (NTCPs) for the organs at risk (ORs) were calculated for comparison. RESULTS: The average root mean square deviation of the differential dose-volume histogram of the breast planning target volume was 4.6, 3.9 and 3.5% and the average mean dose to the IMC was 97.2, 108.0 and 99.6% for the oblique electron, wide split tangent and IMRT techniques, respectively. The average NTCP for the ORs (i.e. heart and lungs) were comparable between the oblique electron and IMRT techniques (or=2%) for the ORs. CONCLUSIONS: The lowest NTCP values were found with the oblique electron and the IMRT techniques. The IMRT technique had the best breast and IMC target coverage.     

Critical appraisal of treatment techniques based on conventional photon beams, intensity modulated photon beams and proton beams for therapy of intact breast.

PURPOSE: To analyse different treatment techniques with conventional photon beams, intensity modulated photon beams, and proton beams for intact breast irradiation for patients in whom conventional irradiation would cause potentially dangerous lung irradiation. MATERIALS AND METHODS: Five breast cancer patients with highly concave breast tissue volume around the lung were considered at planning level in order to assess the suitability of different irradiation techniques. Three-dimensional dose distributions for conventional two-field tangential photon treatment, two-field intensity modulated radiotherapy (IMRT), three-field non-IMRT, three-field IMRT, and single-field proton treatment were investigated, aiming at assessing the possibility to reduce lung irradiation below risk levels. Analysis of dose-volume histograms and related physical and biological parameters (significant minimum, maximum and mean doses, conformity indexes and equivalent uniform dose (EUD)) for planned target volume (PTV) and lung was carried out. Dose plans were compared with the conventional two-field tangential photon technique. RESULTS: PTV coverage was comparable for non-IMRT and IMRT techniques (EUD from 47.1 to 49.4 Gy), and improved with single-field proton treatment (EUD=49.8 Gy). Lung irradiation was reduced, in terms of mean dose, with three-field (9.5 Gy) and proton technique (3.5 Gy), with respect to the conventional two-field treatment (12.9 Gy); also a reduction of the lung volume irradiated at high doses was observed. Better results could be achieved with protons. In addition, cardiac irradiation was also reduced with those techniques. CONCLUSIONS: Geometrically difficult breast cancer patients could be irradiated with a three-field non-IMRT technique thus reducing the dose to the lung which is proposed as standard for this category of patients. Intensity modulated techniques were only marginally more successful than the corresponding non-IMRT treatments, while protons offer excellent results.     

将左心室作为危及器官在左侧乳腺癌保乳术后放疗中的保护心脏作用

目的探索左心室(left ventricle,LV)作为新的危及器官(organ at risk,OAR)在左乳腺癌保乳术后放疗中心脏保护的作用。方法随机选取13例左乳腺癌接受保乳术及术后辅助放疗患者的计划CT图像。由同一个放疗医师勾画靶区和OAR,OAR包括心脏、LV、左右肺和右侧乳腺。每个患者由物理师制定4个治疗计划。所有治疗计划的处方剂量均为50 Gy,25次。比较PTV、心脏、左右肺和右侧乳腺的剂量体积参数。结果与TF计划相比,在IMRT计划中PTV的最大剂量［除了IMRT(H)计划外］和最小剂量有不同程度增加。与IMRT(H)计划相比,在IMRT(H+LV)和IMRT(LV)计划中PTV内的最大剂量分别增加,大于V110 高剂量体积增加。与TF计划相比,在IMRT计划中心脏的平均剂量、中位剂量、V5、V10分别增加0.9%~22.3% (P>0.05)、78.3%~110.6%(P<0.05)、179.3%~209.2%(P<0.05)、24.7%~97.7%。心脏最大剂量、V15、V20分别降低18.6%~36.7%(P<0.05)、7.2%~52.6%、48.3%~79.5%(P<0.05)。左肺在IMRT计划中高剂量体积（大于V17）明显降低,而低剂量体积（小于V12）明显升高。结论左乳腺癌保乳术后IMRT中增加左心室作为OAR可降低心脏照射剂量。     

早期乳腺癌保乳术后全乳调强放射治疗与常规切线野放疗的剂量学比较

目的探讨早期乳腺癌保乳术后全乳调强放射治疗(intensity-modulated radiotherapy,IMRT)的剂量学优势。方法选择6例接受保乳手术的T1N0M0早期乳腺癌病例,其中左侧乳腺癌4例,右侧乳腺癌2例,应用三维调强治疗计划系统为每例患者设计常规切线野与IMRT2种全乳放射治疗计划,处方剂量均为50Gy/25次。用剂量体积直方图(dose volume histograms,DVH)来比较2种计划中计划靶体积(planning target volume,PTV)、危及器官(organs at risks,OARs)的剂量学差异。结果在2种计划中,95%PTV均接受50Gy,99%PTV均接受95%的处方剂量;但在IMRT计划组V110%(接受大于110%处方剂量体积占PTV的百分比)下降了9.1%(46.3%比37.2%,P<0.05);同侧肺的V20(至少接受20Gy照射的肺体积占同侧肺体积的百分比)下降了7.2%(26.8%比18.0%,P<0.05);同侧肺的V30下降了12.0%(23.2%比11.2%,P<0.05);4例左侧乳腺癌患者的心脏V30下降了3.8%(7.0%比3.2%,P<0.05)。结论全乳IMRT在保证靶区覆盖率的前提下,改善了靶区内剂量的均匀性,降低了危及器官的受照剂量及缩小了危及器官的照射体积,尤其是同侧肺、心脏的照射体积,降低放射性肺炎及心血管事件发生的可能。     

Significant reductions in heart and lung doses using deep inspiration breath hold with active breathing control and intensity-modulated radiation therapy for patients treated with locoregional breast irradiation

PURPOSE: To evaluate the heart and lung sparing effects of moderate deep inspiration breath hold (mDIBH) achieved using an active breathing control (ABC) device, compared with free breathing (FB) during treatment with deep tangents fields (DT) for locoregional (LR) irradiation of breast cancer patients, including the internal mammary (IM) nodes (IMNs). To compare the DT-mDIBH technique to other standard techniques and to evaluate the dosimetric effect of intensity-modulated radiation therapy (IMRT). METHODS AND MATERIALS: Fifteen patients (9 left-sided and 6 right-sided lesions) with Stages 0-III breast cancer underwent standard FB and ABC computed tomographic (CT) scans in the treatment position. A dosimetric planning study was performed. In FB, the 9 left-sided patients were planned with a 5-field technique where electron fields covering the IM region were matched to shallow tangents using wedges (South West Oncology Group [SWOG] protocol S9927 technique A). This method was compared with a 3-field DT technique covering the breast and the IMNs (SWOG S9927 technique B). Compensation with IMRT was then compared with wedges for each technique. For the 15 total patients, dosimetric planning using DT with IMRT was then reoptimized on the mDIBH CT data set for comparison. Dose-volume histograms for the clinical target volume (CTV) (including the IMNs), planning target volume (PTV), ipsilateral and contralateral breast, and organs at risk (OAR) were analyzed. In addition, normal tissue complication probabilities (NTCP) for lung and heart, mean lung doses, and the number of monitor units (MUs) for a 1.8 Gy fraction were compared. RESULTS: For the 9 left-sided patients, the mean percentage of heart receiving more than 30 Gy (heart V30) was lower with the 5-field wedged technique than with the DT wedged technique (6.8% and 19.1%, respectively, p < 0.004). For the DT technique, the replacement of wedges with IMRT slightly diminished the mean heart V30 to 16.3% (p < 0.51). The introduction of mDIBH to the DT-IMRT technique reduced the heart V30 by 81% to a mean of 3.1% (p < 0.0004). Compared with 5-field IMRT, DT-IMRT with mDIBH reduced the heart V30 for 6 of the 9 patients, entirely avoiding heart irradiation in 2 of these 6 patients. For DT-IMRT, mDIBH reduced the mean lung dose and NTCP to levels obtained with the 5-field IMRT technique. For the 15 patients planned with DT-IMRT in FB, the use of mDIBH reduced the mean percentage of both lungs receiving more than 20 Gy from 20.4% to 15.2% (p < 0.00007). With DT-IMRT, more than 5% of the contralateral breast received more than 10 Gy for 6 of the 9 left-sided patients in FB, 3 of those 9 patients in mDIBH, and only 1 of those 9 patients planned with 5 fields. The mean % of the PTV receiving more than 55 Gy (110% of the prescribed dose) was 36.4% for 5-field wedges, 33.4% for 5-field IMRT, 28.7% for DT-wedges, 12.5% for DT-IMRT, and 18.4% for DT-IMRT mDIBH. The CTV remained covered by the 95% isodose in all the DT plans but one (99.1% of the volume covered). DT-wedges required more MUs than DT-IMRT (mean of 645 and 416, respectively, p < 0.00004). CONCLUSION: mDIBH significantly reduces heart and lung doses when DT are used for LR breast irradiation including the IMNs. Compared with shallow tangents matched with electrons, DT with mDIBH reduces the heart dose (in most patients) and results in comparable lung toxicity parameters, but may increase the dose to the contralateral breast. IMRT improves dose homogeneity, slightly reduces the dose to the heart, and diminishes the number of MUs required.     

大分割模式下左侧乳腺癌保乳术后调强放疗方式的探索

目的:比较左侧乳腺癌保乳术后大分割放疗时,野中野正向调强（field-in-field intensity modulated radiation therapy,FIF-IMRT）、逆向调强（intensity modulated radiation therapy,IMRT）两种模式对改善靶区剂量分布和保护正常组织的差异。方法:对30例左侧乳腺癌保乳术后患者予以CT定位,分别制定FIF-IMRT及IMRT二种照射计划,总剂量均为42.65 Gy,共照射16次。分别比较两组计划的靶区剂量分布、危及器官,如心脏、肺脏、脊髓等所受剂量以及加速器总跳数（accelerator monitor unit,MU）的差异。结果:FIF-IMRT与IMRT组PTV(planning target volume)的Dmax分别为4 762.35 cGy（4 710.08,4 829.10）cGy、4 714.60 cGy（4 659.55,4 740.85）cGy（P=0.001）,均匀性指数分别为0.10（0.09,0.11）和0.09（0.08,0.10）（P=0.008）;在危及器官受量方面,FIF-IMRT组较IMRT组明显降低心脏V5、V10和左肺V5、V10（P值分别为<0.001、<0.001、0.003、0.014）,右乳Dmax、Dmean和脊髓Dmax、DmeanFIF-IMRT组均显著低于IMRT组（P值分别为0.048、0.044、<0.001、<0.001）。FIF-IMRT组MU低于IMRT组（P=0.001）。结论:两种大分割调强模式均能满足左侧乳腺癌保乳术后的治疗要求。IMRT提高靶区剂量分布均匀性,但FIF-IMRT能更好降低心脏和左肺V5、V10等低剂量照射范围,且对机器损耗更小,可能是更好的选择。     

Number and orientation of beams in inversely planned intensity-modulated radiotherapy of the female breast and the parasternal lymph nodes

Intensity-modulated radiotherapy (IMRT) provides better sparing of normal tissue. We evaluated the optimum beam configuration for IMRT based on inverse treatment planning in adjuvant radiotherapy for breast cancer in a case of left-sided tumor. In addition to radiotherapy planning with the conventional technique of tangential wedged 6-MV photon beams and an oblique 15-MeV electron beam, we performed inversely planned IMRT with the step-and-shoot-technique. Dose calculation was carried out using the treatment planning system Virtuos with the inverse optimization module KonRad adapted to it. IMRT plans were generated for 2 to 16 beams. The results were compared with conventional techniques. For a maximum treatment time of 20 minutes, it is shown that IMRT with 12 modulated photon beams and 7 intensity steps is best suited for treatment in the presented case. Compared with a conventional technique with photons combined with electrons, dose conformality and homogeneity of the planning target volume was increased. The mean heart dose was reduced from 9.1 Gy to 6.1 Gy. The volume of heart irradiated with a dose higher than 30 Gy was reduced from 7.6% to 1.9%, and the volume of the left lung from 13.6% to 11.5% as well. Inverse optimization for IMRT with multiple beams is feasible in the adjuvant treatment of breast cancer. Because of the reduction of the high-dose area of a substantial cardiac volume, it is superior to conventional techniques in cases where the parasternal lymph nodes should be integrated into the target volume. Here, a clinical advantage might be detectable.     

乳腺癌保乳术后调强放疗与常规放疗的剂量学比较

 目的　探讨早期乳腺癌保乳术后全乳适形调强放射治疗（IMRT）的剂量学优势。方法　选择10例接受保乳手术的Tis~2N0M0早期乳腺癌病例,其中左侧乳腺癌6例,右侧乳腺癌4例,应用三维治疗计划系统（3D-TPS）为每位患者设计两种全乳放射治疗计划,即切线野常规计划与IMRT计划,处方剂量均为50 Gy／25次。用剂量体积直方图（DVH）来比较两种计划中计划靶体积（PTV）、危及器官（OARS）的剂量学差异。结果　靶区覆盖率在两种计划中相似,分别为97.83 %、97.61 %,与常规计划相比IMRT计划的PTV接受＜95 %处方剂量与＞103 %处方剂量的体积百分比之和（IHI） 从25.42 %减少到2.71 %,PTV接受至少105 %处方剂量照射的体积百分比（V105 %）从25.79 %减少到1.08 %,IMRT计划改善IHI和减少V105 %的平均值,在PTV较大的患者中更明显。左侧乳腺癌患者心脏的平均剂量（Dmean）从6.72 Gy减少到4.95 Gy、心脏接受30 Gy照射的体积百分比（V30）从7.23 %减少到1.04 %。所有患者同侧肺的Dmean从9.19 Gy减少到7.65 Gy、至少接受20 Gy 照射的体积百分比（V20）从22.34 %减少到20.18 %。对侧乳腺Dmean从5.12 Gy减少到3.52 Gy,对侧肺Dmean从2.76 Gy减少到1.79 Gy。右侧患者肝脏Dmean从7.23 Gy减少到1.04 Gy。结论　全乳IMRT的剂量学优势主要是在保证靶区覆盖率的前提下,显著改善了靶区剂量分布的均匀性,并在一定程度上降低OARS的受照剂量与容积,乳房体积大的病例可以通过IMRT获得更好的剂量学结果。     

同时性双侧乳腺癌保乳术后放疗技术和近期疗效分析

目的 探讨同时性双侧乳腺癌整体等中心切线野混合调强技术的剂量特点及疗效。方法 纳入14例同时性双侧乳腺癌保乳术后双侧全乳±瘤床加量放疗患者。采用等中心切线野混合调强技术进行双乳整体放疗(50Gy分25次或43.5Gy分15次)。分析计划的覆盖度、均匀性及临床近期疗效。结果 全组患者放疗计划总野数为8~11个,其中调强野为4~7个。全乳计划靶区均达95%,平均瘤床覆盖度在X线同步补量组分别为(95.54±1.33)%(左)及(94.19±1.03)%(右),在电子线序贯补量组为(90.25±8.79)%(左)及(85.28±8.35)%(右)。平均双肺V20为(16.69±3.90)%,平均心脏Dmean为5.48Gy。全组3例出现2级急性皮肤反应,无≥2级的放射性肺炎发生。中位随访至30.1个月时,11例美容效果为优,无一复发。结论 双乳腺癌保乳术后采用整体等中心切线野混合调强技术安全可靠。