左侧乳腺癌保乳术后采用深吸气屏气放疗的心脏剂量学分析

目的 探究左侧乳腺癌保乳术后放疗患者采用深吸气屏气(DIBH)技术对心脏剂量的改善情况,分析可能影响心脏剂量的解剖因素。方法 前瞻性入组 15例左侧乳腺癌保乳术后行全乳放疗患者,符合呼吸控制要求。分别在自由呼吸(FB)和DIBH状态下进行2次模拟CT扫描,在DIBH图像上制定全乳放疗计划。比较FB和DIBH状态下心肺位置和体积变化以及心肺剂量差异,探究FB状态下各解剖因素与心脏剂量的相关性。对计数资料组间行非参数Wilcoxon秩和检验,双变量相关分析采用Pearson法。结果 DIBH与FB状态下心脏体积相似(P=0.773),而双肺体积明显增加(P=0.001)。心脏、冠脉左前降支、左心室、右心室和左肺 Dmean、Dmax和V5—V40均明显降低(P<0.05)。DIBH使肺体积增加越显著,心脏平均剂量下降幅度越大。FB状态下乳腺体积、心肺体积比、乳腺下界与心脏下界距离、最大心脏切缘距离分别与心脏剂量呈线性相关,其中心肺体积比、最大心脏切缘距离与心脏剂量具有独立相关性。结论 左侧乳腺癌保乳术后采用DIBH技术行全乳放疗较FB状态明显降低心肺剂量。肺体积的变化是改善心脏相对解剖位置的基础。心肺体积比、最大心脏切缘距离或许可以作为进行DIBH技术治疗的参考标准。     

Patient-Specific Heart Constraint: A Tool for Optimization and Evaluation of Mean Heart Dose in Breast Cancer Patients

PurposeOur institution introduced a patient-specific heart constraint (PSHC) and a mean heart dose (MHD) constraint of 4 Gy for all patients receiving breast radiation therapy (RT) with a simultaneous boost (SIB). This was introduced as a method to calculate the predicted MHD before optimizing IMRT fields. We sought to determine whether the introduction of a PSHC reduced MHD, while maintaining optimally dosed treatment plans.Material/MethodsPatients were retrospectively divided into 2 groups, pre- and postintroduction of the PSHC. The breast and SIB Planning Target Volumes (PTVs) were prescribed to 50 Gy and 57 Gy, respectively, in 25 fractions. Plans were generated using a hybrid IMRT technique, 30 Gy using an open tangential field arrangement, and 27 Gy using IMRT fields. The PSHC was calculated using MHD of open tangential field × 2. A paired t test compared PTV coverage and heart doses between cohorts (P < .05 significant).ResultsA total of 264 patients were included (138 pre-PSHC and 126 post-PSHC) with 137 right-sided and 127 left-sided treatments. MHD was significantly reduced across both right-sided (–0.4 Gy, P < .0001) and left-sided (–1.2 Gy, P < .0001) treatments overall. Left-sided treatments were further examined between free breathing and deep inspiration breath-hold (DIBH). DIBH showed reduction in MHD, although it was not significant (–0.46 Gy, P = .34). Heart V5 Gy showed reduction in right-sided (–1%, P = .002) and left-sided (–9.2%, P < .0001) treatments overall. Left-sided free breathing showed significant reduction (–8.8%, P < .0001), and DIBH also showed significant reduction (–5.1%, P = .0034). Tumor bed doses remained above the 54.15 Gy (95% of 57 Gy) threshold for all plans.ConclusionIntroduction of a PSHC can reduce MHD and V5 Gy for patients receiving whole breast RT with SIB while maintaining optimally dosed plans, with the greatest benefit shown for left-sided, free-breathing treatments.     

DIBH技术对纵隔淋巴瘤累及部位放疗靶区与OAR受量影响

目的 探讨深吸气屏气(DIBH)技术对纵隔淋巴瘤放疗靶区和正常组织受量影响。方法 前瞻性采集连续收治的5例Ⅰ、Ⅱ期纵隔淋巴瘤病例。采用受累部位照射和蝴蝶野设野原则,对比DIBH和自由呼吸(FB)扫描时靶区绝对体积变化、重要OAR绝对剂量体积和相对剂量-体积差别。配对t检验差异。结果 5例中位年龄30岁。与FB相比DIBH时靶区绝对体积化疗前GTV缩减29.4 cm³(P=0.006),PTV缩减322 cm³(P=0.005);肺绝对体积平均增大1456 cm³(P=0.001),心脏宽度缩小1.3 cm (P=0.012)。DIBH时心脏和肺D_mean显著降低(心脏为8.5 Gy∶11.6 Gy,P=0.022;肺为7.6 Gy∶11.6 Gy,P=0.000)。比较受一定水平照射的绝对体积时,心脏在高剂量水平V₁₅及以上显著降低(P均<0.05)。DIBH时肺和心脏相对百分比在所有剂量水平(V₅—V₃₅)均显著小于FB (P均<0.05)。结论 纵隔淋巴瘤放疗,DIBH技术能显著缩小PTV,增加肺体积,且显著降低心肺D_mean和V₅—V₃₅水平的相对剂量-体积参数。     

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.

     

深吸气屏气和自由呼吸状态在乳腺托架固定下全乳调强放疗中的摆位误差研究

目的 比较乳腺癌保乳术后深吸气屏气(DIBH)与自由呼吸(FB)状态下放疗的摆位误差。方法 回顾性分析 2016年4月至 2018年6月在中国医学科学院肿瘤医院接受保乳术后采用DIBH技术行全乳放疗的左侧乳腺患者 30例,并选取 30例自由呼吸状态下接受全乳放疗的乳腺癌患者作为对照。比较放疗计划系统CT图像与放射治疗期间锥形束CT的位移,确定摆位误差,并计算临床靶体积(CTV)外扩至计划靶体积(PTV)的边界。摆位误差的比较采用t检验。结果 全组患者共拍摄锥形束CT图像318套,平均每人(5.1±1.1)套。FB患者摆位误差在x轴、y轴和z轴的位移分别为(2.2±1.7) mm,(3.1±2.5) mm,(3.3±2.3) mm。DIBH患者摆位误差在x轴、y轴和z轴的位移分别为(2.1±1.6) mm,(2.6±1.7) mm,(2.5±2.1) mm。在y轴和z轴方向,DIBH患者的位移显著小于FB患者(P=0.015、0.004),两组患者在x轴方向位移无明显差别(P=0.294)。DIBH患者CTV至PTV在x轴、y轴和z轴方向外扩边界分别为6.2、7.3、7.8mm。DIBH组放疗第一周与后续放疗、不同体重指数(BMI)的摆位误差无差别。结论 乳腺癌保乳术后全乳放疗时,DIBH技术摆位误差小于FB,推荐DIBH放疗的CTV至PTV的外扩边界为 6~8mm。     

Comparison of setup errors between deep inspiration breath hold and free breathing for whole breast irradiation

Objective To compare the setup errors between deep inspiration breath hold (DIBH) and free breathing (FB) for breast cancer patients who were treated with whole breast irradiation (WBI) after breast conserving surgery (BCS). Methods In this retrospective analysis, 30 breast cancer patients receiving WBI following BCS using DIBH in National Cancer Center/ Chinese Academy of Medical Sciences, an 30 patients treated with WBI using FB were enrolled as comparator.The kilovoltage cone-beam computed tomography (CBCT) was performed to evaluate and reduce setup errors. The optimal margins from clinical target volume (CTV) to planning target volume (PTV) for DIBH were estimated. The differences of setup errors between two techniques were compared using independent two-sample t-test. Results A total of 318 sets of CBCT images were acquired, with (5.1±1.1) sets per patient on average. The setup errors along the three translational directions (laternal, longitudinal and vertical) were (2.1±1.6) mm,(2.6±1.7) mm and (2.5±2.1) mm for DIBH, and (2.2±1.7) mm,(3.1±2.5) mm and (3.3±2.3) mm for FB, respectively. Compared with FB, DIBH significantly reduced setup errors in the longitudinal (P=0.015) and vertical (P=0.004) directions, whereas the setup errors in the lateral direction did not significantly differ (P=0.294). The optimal margins from CTV to PTV using DIBH were 6.2 mm, 7.3 mm and 7.8 mm, respectively.In the DIBH group, treatment fractions at the beginning and higher body mass index (BMI) did not associate with larger set-up deviation. Conclusions DIBH technique yields less setup errors than FB for breast cancer patients treated with WBI after BCS. The CTV-PTV margins of 6-8 mm are recommended for DIBH.     

深吸气屏气技术在左侧乳腺癌保乳术后动态容积旋转调强放疗中的剂量学分析

目的:比较深吸气屏气(deep inspiration breath-hold,DIBH)和自由呼吸(free breathing,FB)两种呼吸模式在左侧乳腺癌保乳术后动态容积旋转调强（volumetric modulated arc therapy,VMAT）放疗中的剂量学差异,探寻左侧乳腺癌保乳术后放疗最佳呼吸模式。方法:选取11例左侧乳腺癌保乳术后女性患者,分别在DIBH-CT和FB-CT图像上设计切线弧t-VMAT计划。结果:DIBH呼吸模式下心脏V5、V10、V20、V30、Dmean、左冠状动脉前降支Dmean、左肺Dmean、右肺V5、Dmean及右侧乳腺V5、Dmean均低于FB呼吸模式,且差异均有统计学意义（P均＜0.05）,其中心脏、左冠状动脉前降支LAD及左肺平均剂量分别下降26.2%、47.7%和11.8%。结论:DIBH呼吸模式显著降低了心脏及左冠状动脉前降支等危及器官的受照剂量,采用t-VMAT计划缩短了深吸气屏气技术的治疗时间,提高了患者舒适度,更好的保证治疗顺利进行。     

Benefit of Deep Inspiratory Breath Hold for Right Breast Cancer When Regional Lymph Nodes Are Irradiated

BackgroundAlthough deep inspiratory breath-hold (DIBH) is routinely used for left-sided breast cancers, its benefits for right-sided breast cancer (rBC) have yet to be established. We compared free-breathing (FB) and DIBH treatment plans for a cohort of rBC undergoing regional nodal irradiation (RNI) to determine its potential benefits.Methods and MaterialsrBC patients considered for RNI (internal mammary nodal chains, supraclavicular field, with or without axilla) from October 2017 to May 2020 were included in this analysis. For each patient, FB versus DIBH plans were generated and dose volume histograms evaluated the following parameters: mean lung dose, ipsilateral lung V₂₀/V₅ (volumes of lung receiving 20 Gy and 5 Gy, respectively); mean heart dose and heart V₅ (volumes of heart receiving 5 Gy); liver V_{20 absolute} /V_{30 absolute} (absolute volume of liver receiving 20 Gy and 30 Gy, respectively), liver D_max, and total liver volume irradiated (TVI_liver). The dosimetric parameters were compared using Wilcoxon signed-rank testing.ResultsFifty-four patients were eligible for analysis, comparing 108 FB and DIBH plans. DIBH significantly decreased all lung and liver parameters: mean lung dose (19.7 Gy-16.2 Gy, P < .001), lung V₂₀ (40.7%-31.7%, P < .001), lung V₅ (61.2%-54.5%, P < .001), TVI_liver (1446 cc vs 1264 cc; P = .006) liver D_max (50.2 Gy vs 48.9 Gy; P = .023), liver V₂₀ (78.8-23.9 cc, P < .001), and liver V₃₀ (58.1-14.6 cc, P < .001) compared with FB. DIBH use did not significantly improve heart parameters, although the V_5Heart trended on significance (1.25-0.6, P = .067).ConclusionsThis is the largest cohort to date analyzing DIBH for RNI-rBC. Our findings demonstrate significant improvement in all lung and liver parameters with DIBH, supporting its routine consideration for rBC patients undergoing comprehensive RNI.     

Cardiotoxic effects of tangential breast irradiation in early breast cancer patients: the role of irradiated heart volume

PURPOSE: To assess the risk of cardiovascular disease (CVD) after postlumpectomy irradiation restricted to tangential fields. METHODS AND MATERIALS: We assessed the incidence of CVD in 1601 patients with T1-2N0 breast cancer (BC) treated with breast tangentials in five different hospitals between 1980 and 1993. Patients treated with radiation fields other than breast tangentials and those treated with adjuvant chemotherapy were excluded. For patients with left-sided BC, maximum heart distance (MHD) was measured on the simulator films as a proxy for irradiated heart volume. Risk of CVD by laterality and MHD categories was evaluated by Cox proportional hazards regression analysis. RESULTS: Follow-up was complete for 94% of the patients, and median follow-up was 16 years. The incidence of CVD overall was 14.1%, of ischemic heart disease 7.3%, and for other types of heart disease 9.2%, with a median time to event of 10 to 11 years. The incidence of CVD was 11.6% in patients with right-sided BC, compared with 16.0% in left-sided cases. The hazard ratio associated with left-sided vs. right-sided BC was 1.38 (95% confidence interval [CI], 1.05-1.81) for CVD overall, 1.35 (95% CI, 0.93-1.98) for ischemic heart disease , and 1.53 (95% CI, 1.09-2.15) for other heart disease, adjusted for age, diabetes, and history of CVD. The risk of CVD did not significantly increase with increasing MHD. CONCLUSIONS: Patients irradiated for left-sided BC with tangential fields have a higher incidence of CVD compared with those with right-sided cancer. However, the risk does not seem to increase with larger irradiated heart volumes.     

深吸气屏气技术在左侧乳腺癌术后放疗中的应用（附41例）

目的:探讨深吸气屏气(deep inspiration breath hold，DIBH)技术在左侧乳腺癌术后放射治疗中的剂量学优势。方法:对澳门镜湖医院在2016年4月至2017年12月期间连续收治的41例左侧乳腺癌患者，接受术后放疗的资料进行总结，比较DIBH和自由呼吸（free breath，FB）两种呼吸模式下放疗的剂量学差异，包括靶区适形性（conformity index，CI）和均匀性（homogeneity index，HI）参数，肺、心脏、左侧冠状动脉前降支（LAD）以及右侧乳腺剂量比较。结果:DIBH和FB两种模式下心脏的平均剂量、左侧冠状动脉前降支平均剂量、左肺V20有显著性差别，分别是（4.92±1.93）Gy vs （6.53±2.30）Gy（P<0.001）、（18.71±9.00）Gy vs （27.21±8.81）Gy（P<0.001）、（23.42±6.67）% vs （28.03±8.68）%（P<0.001）。单纯全乳/胸壁放疗与全乳/胸壁+区域淋巴结放疗两组在DIBH模式下，左肺V20下降的百分比分别为16.53%和24.86%，差异有统计学意义（P<0.05）。DIBH和FB的靶区适形性和均匀性均无差异。结论:采用DIBH可以显著减少心脏、冠状动脉和肺等重要器官的照射。无论是单纯乳腺/胸壁放疗还是合并区域淋巴结放疗，采用DIBH技术均可以临床获益。     

TROG 14.04: Multicentre Study of Feasibility and Impact on Anxiety of DIBH in Breast Cancer Patients

AimsThe aim of TROG 14.04 was to assess the feasibility of deep inspiration breath hold (DIBH) and its impact on radiation dose to the heart in patients with left-sided breast cancer undergoing radiotherapy. Secondary end points pertained to patient anxiety and cost of delivering a DIBH programme.Materials and methodsThe study comprised two groups – left-sided breast cancer patients engaging DIBH and right-sided breast cancer patients using free breathing through radiotherapy. The primary end point was the feasibility of DIBH, defined as left-sided breast cancer patients' ability to breath hold for 15 s, decrease in heart dose in DIBH compared with the free breathing treatment plan and reproducibility of radiotherapy delivery using mid-lung distance (MLD) assessed on electronic portal imaging as the surrogate. The time required for treatment delivery, patient-reported outcomes and resource requirement were compared between the groups.ResultsBetween February and November 2018, 32 left-sided and 30 right-sided breast cancer patients from six radiotherapy centres were enrolled. Two left-sided breast cancer patients did not undergo DIBH (one treated in free breathing as per investigator choice, one withdrawn). The mean heart dose was reduced from 2.8 Gy (free breathing) to 1.5 Gy (DIBH). Set-up reproducibility in the first week of treatment assessed by MLD was 1.88 ± 1.04 mm (average ± 1 standard deviation) for DIBH and 1.59 ± 0.93 mm for free breathing patients. Using a reproducibility cut-off for MLD of 2 mm (1 standard deviation) as per study protocol, DIBH was feasible for 67% of DIBH patients. Radiotherapy delivery using DIBH took about 2 min longer than for free breathing. Anxiety was not significantly different in DIBH patients and decreased over the course of treatment in both groups.ConclusionAlthough DIBH was shown to require about 2 min longer per treatment slot, it has the potential to reduce heart dose in left-sided breast cancer patients by nearly a half, provided careful assessment of breath hold reproducibility is carried out.     

Resource requirements and reduction in cardiac mortality from deep inspiration breath hold (DIBH) radiation therapy for left sided breast cancer patients: A prospective service development analysis

Introduction

Use of deep inspiration breath hold (DIBH) radiation therapy may reduce long-term cardiac mortality. The resource and time commitments associated with DIBH are impediments to its widespread adoption. We report the dosimetric benefits, workforce requirements, and potential reduction in cardiac mortality when DIBH is used for left-sided breast cancers.

Reproducibility of the abdominal and chest wall position by voluntary breath-hold technique using a laser-based monitoring and visual feedback system

PURPOSE: The voluntary breath-hold (BH) technique is a simple method to control the respiration-related motion of a tumor during irradiation. However, the abdominal and chest wall position may not be accurately reproduced using the BH technique. The purpose of this study was to examine whether visual feedback can reduce the fluctuation in wall motion during BH using a new respiratory monitoring device. METHODS AND MATERIALS: We developed a laser-based BH monitoring and visual feedback system. For this study, five healthy volunteers were enrolled. The volunteers, practicing abdominal breathing, performed shallow end-expiration BH (SEBH), shallow end-inspiration BH (SIBH), and deep end-inspiration BH (DIBH) with or without visual feedback. The abdominal and chest wall positions were measured at 80-ms intervals during BHs. RESULTS: The fluctuation in the chest wall position was smaller than that of the abdominal wall position. The reproducibility of the wall position was improved by visual feedback. With a monitoring device, visual feedback reduced the mean deviation of the abdominal wall from 2.1 +/- 1.3 mm to 1.5 +/- 0.5 mm, 2.5 +/- 1.9 mm to 1.1 +/- 0.4 mm, and 6.6 +/- 2.4 mm to 2.6 +/- 1.4 mm in SEBH, SIBH, and DIBH, respectively. CONCLUSIONS: Volunteers can perform the BH maneuver in a highly reproducible fashion when informed about the position of the wall, although in the case of DIBH, the deviation in the wall position remained substantial.     

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.     

The benefit of deep inspiration breath hold: evaluating cardiac radiation exposure in patients after mastectomy and after breast-conserving surgery

Background

This study aims to evaluate the reduction of cardiac radiation dose and volume with deep inspiration breath hold (DIBH) technique compared to free breathing (FB) in patients with left-sided breast cancer. The study also aims to evaluate whether the benefits of DIBH vary in patients who had whole breast radiotherapy (RT) after breast-conserving surgery (BCS) and those who had chest wall RT post-mastectomy (M).

Methods

FB and DIBH plans were generated for 15 consecutive post-BCS patients and 17 post-M patients who underwent RT with DIBH using varian real-time position management (RPM) system. Cardiac shields were used in all post-BCS plans, provided that clinical treatment volume coverage was not compromised, while chest wall coverage took priority in post-M plans. The prescribed dose was 50 Gy in 25 fractions for the whole breast or the chest wall. Parameters of interest were cardiac V5, mean LAD dose, maximum LAD dose, and mean heart dose. The impact of DIBH was compared in post-BCS and post-M patients using paired t tests. To gauge clinically meaningful outcome, the proportion of patients with V5 < 5 % and mean cardiac dose <2 Gy were compared using McNemar’s test.

Results

DIBH decreased V5 by an absolute 4.5 % (2.3 vs. 6.8 %; p < 0.0001) in post-M group, and by an absolute 2.4 % (1.3 vs. 3.7 %; p = 0.0028) in post-BCS group. DIBH decreased the mean heart dose by 107.0 cGy (127.4 vs. 234.4 cGy; p = 0.0002) in post-M group, and by 58.9 cGy (82.2 vs. 141.1 cGy; p = 0.0012) in post-BCS group. DIBH decreased mean LAD by 1201.6 cGy (670 vs. 1872.5 cGy; p = 0.0006) in post-M group, and by 799.0 cGy (425.3 vs. 1224.3 cGy; p = 0.0003) in post-BCS group. DIBH also decreased max LAD dose by 1244.3 cGy (2776.0 vs. 4020.3 cGy; p = 0.0014) in post-M group, and by 1856.3 cGy (1898.7 vs. 3754.9 cGy; p = 0.0005) in post-BCS group. In post-BCS group, cardiac V5 < 5 % was achieved in 10/15 (67 %) FB patients, and in 15/15 (100 %) DIBH patients (p = 0.002), and mean heart dose <2 Gy was achieved in 12/15 (80 %) FB patients and in 15/15 (100 %) DIBH patients (p < 0.001). This compares with post-M group, in which V5 < 5 % was achieved in 6/17 (35 %) FB patients and in 16/17 (94 %) DIBH patients (p = 0.05), and mean heart dose <2 Gy was achieved in 7/17 FB (41 %) an 16/17 DIBH patients (94 %) (p = 0.03).

Conclusion

The results of this study suggest that there is considerable reduction in cardiac exposure in most patients with DIBH compared to FB, although less reduction is observed in the post-BCS patients. The use of cardiac shields and collimators/gantry adjustments, more readily applicable for post-BCS cases, may limit the additional benefits of DIBH. In an environment where DIBH availability is limited, the result of this study supports the preferential use of DIBH in post-M patients over post-BCS patients.