Left-sided Breast Irradiation Research Articles

Dosimetric and radiobiological advantages from deep inspiration breath-hold and free breath technique for left-sided breast radiation using 3DCRT, IMRT and Rapid Arc methods-a complete assessment.

The verification and use of the best treatment approach using 3D conformal radiation therapy (3DCRT), intensity modulated radiation therapy (IMRT) and Rapid Arc methods for left breast radiation with dosimetric and radiobiological characteristics. The use of custom-built Python software for the estimation and comparison of volume, mean dose, maximum dose, monitor units and normal tissue integral dose along with radiobiological parameters such as NTCP, tumor control probability, equivalent uniform dose and LKB's effective volume from 3DCRT, IMRT and Rapid Arc planning with deep inspiration with breath holding (DIBH) and free breadth (FB) techniques. Volume growth of three-fourth in DIBH compared with FB causes a decrease in cardiac doses and complications because the left lung expands, pulling the heart away from the chest wall and the treatment area. A tiny area of the left lung was exposed during treatment, which reduced the mean dose. There was little difference in the treatment approaches because the spinal cord was immobile in both techniques. Rapid Arc is the unmatched modality for left-sided breast irradiation with significant patient breath-hold, as shown by the comparison of dosimetric and radiobiological parameters from treatment techniques with a deep inspiration breath-hold approach.

Comparing breath hold versus free breathing irradiation for left-sided breast radiotherapy by PlanIQ™

BackgroundBreast cancer is the most widespread cancer in women and young women worldwide. Moving towards customised radiotherapy, balancing the use of the available technology with the best treatment modality may not be an easy task in the daily routine. This study aims to evaluate the effectiveness of introducing IQ-feasibility into clinical practice to support the decision of free-breathing (FB) versus breath-hold (BH) left-sided breast irradiations, in order to optimise the technology available and the effectiveness of the treatment.MethodsThirty-five patients who received 3D radiotherapy treatment of the left breast in deep-inspiration BH were included in this retrospective study. Computed tomography scans in FB and BH were acquired for each patient; targets contoured in both imaging datasets by an experienced radiation oncologist, and organs at risk delineated using automatic segmentation software were exported to PlanIQ™ (Sun Nuclear Corp.) to generate feasibility dose volume histogram (FDVHs). The dosimetric parameter of BH versus FB FDVH, and BH clinical dataset versus BH FDVH were compared.ResultsA total of 30 patients out of 35 patients analysed, presented for the BH treatments a significant reduction (p < 0.05) in the heart mean dose (Dm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{D}}}_{{\ ext{m}}}$$\\end{document}), volume receiving 5 Gy (V5Gy\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{V}}}_{5{\ ext{Gy}}}$$\\end{document}) and 20 Gy (V20Gy\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{V}}}_{20{\ ext{Gy}}}$$\\end{document}), of 35.7%, 54.5%, and 2.1%, respectively; for the left lung, a lower reduction was registered and significant only for V5Gy\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{V}}}_{5{\ ext{Gy}}}$$\\end{document} (21.4%, p = 0.046). For the remaining five patients, the FDVH cut-off points of heart and lung were superimposable with differences of less than 1%. Heart and left lung dosimetric parameters of the BH clinical plans are located in the difficult zone of the FDVH and differ significantly (p < 0.05) from the corresponding parameters of the FDVH curves delimiting this buffer area between the impossible and feasible zones, respectively.ConclusionThe use of PlanIQTM as a decision-support tool for the FB versus BH treatment delivery modality allows customisation of the treatment technique using the most appropriate technology for each patient enabling accurate management of available technologies.

The Impact of Deep Inspiration Breath Hold (DIBH) Implementation on the Hybrid Technique in Left-Sided Whole Breast Irradiation: A Dosimetric Characteristic Study of 3D-CRT Hybrid VMAT in DIBH and Free Breathing Conditions, and VMAT in Free Breathing Conditions.

To investigate the impact of DIBH for heart sparing effect on left sided breast postoperative whole breast irradiation by comparing the dosimetric characteristics of 3D-CRT hybrid VMAT and pure VMAT treatment planning under DIBH condition. The primary CT data sets from previously treated left sided early breast cancer were used for pure volumetric arc therapy (VMAT) technique re-planning for the dosimetric characteristics comparison. A treatment plan of 3D-CRT hybrid VMAT technique was re-planned on the free breath (FB) condition for the investigation of the dosimetric characteristics comparison on DIBH condition. The prescribed dose for all the treatment plans was 42.5Gy in 16 fractions. All plans were optimized to cover 100% of the PTV by 95% of prescribed dose. The dosimetric differences among the 3 treatment plans for the 20 patients were analyzed using Wilcoxon signed-rank test, with p value<0.05 considered statistically significant. 3D-CRT hybrid VMAT using DIBH technique yielded the best results on the conformity index (CI) and homogeneity index (HI). By comparing this 3D-CRT hybrid VMAT technique using FB and DIBH technique, the mean heart dose (MHD) was reduced from 5.38Gy to 1.65Gy, respectively (p =0.001) and the left anterior descending coronary artery (LAD)0.03cc dose was reduced from 27.87Gy to 9.41Gy, respectively (p =0.001). 3D-CRT hybrid VMAT using DIBH technique significantly reduced the V5, V20 and D mean of the ipsilateral lung and D mean of the contralateral lung. The D5 of right breast was significantly reduced by 3D-CRT hybrid VMAT compared with VMAT using DIBH technique. The incorporation of DIBH into 3D-CRT hybrid VMAT technique provides the best benefits for the heart and the OAR with respect to the radiation dose-sparing effect without compromising the target conformity and homogeneity in the treatment planning.

Reducing Racial Disparities in Breast Cancer Treatment

Racial disparities in breast cancer screening, treatment, and outcomes are well established. A recent multi-institutional paper showed a higher mean heart dose (MHD) in Black women and other minorities compared to White women who underwent left-sided breast or chest wall irradiation. We evaluated the MHD of women treated in our institution and investigated whether institution-wide measures can mitigate disparities. We identified 509 consecutively treated female patients from 2012 to 2021 who received left-sided breast or chest wall irradiation (with or without regional nodal irradiation). Medical records were queried to report cardiac dosimetry across various racial groups. Details regarding the use of active breathing control (ABC), breast size, internal mammary nodal irradiation, and whether the patient's treatment plan met the departmental boarding pass requirement and was prospectively presented at departmental peer review were noted. MHD were noted in absolute values and 2-Gy equivalent doses (EQD2). Kruskal-Wallis test was used to analyze differences in MHD between racial groups. Univariate and multivariable Cox regression analyses were performed to determine association of MHD with other factors. MHD was similar across racial groups; 1.38 Gy (1.12, 2.02) in Black women, 1.35 Gy (1.02, 1.97) in White women, and 1.39 Gy (1.07, 2.01) in others with an EQD2 of 0.71, 0.70 and 0.72 (P = 0.6). Rates of the use of hypofractionation, a cavity boost, regional nodal irradiation, internal mammary nodal irradiation, meeting departmental boarding pass requirement, and peer review of treatment plan before starting treatment were similar across all racial groups. The use of ABC was 83% in White women, 75% in Black women and 62% in other races (P = 0.005). The difference in ABC use was attributed to a higher rate of volumetric modulated arc therapy treatment in other races (33%). Median breast size was 1904 cc in Black women, 1504 cc in White women, and 1331 cc in other racial groups (P = 0.001). On univariate and multivariate analysis, MHD differed with IMN treatment, boost and use of ABC but remained similar across racial groups and varying breast size. Despite anatomical differences such as breast size, achieving similar cardiac dose is feasible across racial groups by uniformly utilizing ABC for left sided breast or chest wall irradiation, applying standardized boarding pass constraints and peer review of all cases. Further studies to identify factors that may lead to differences in the rates of cardiac morbidity among racial groups are warranted.

OC-0766 Gain from respiratory gating in left-sided partial breast irradiation in the DBCG PBI trial

OC-0766 Gain from respiratory gating in left-sided partial breast irradiation in the DBCG PBI trial

Evaluation of the voluntary deep inspiration breath-hold reproducibility in left-sided breast radiotherapy.

Voluntary deep inspiration breath hold (v-DIBH) reduces cardiac dose during left-sided breast irradiation. The purpose of this study is to evaluate the reproducibility and variability of breath-hold level (BHL) using breath-hold curves and lateral kV setup images together. A retrospective analysis of 30 left breast cancer patients treated using the v-DIBH technique in our department is performed. The BHL difference is measured from breath hold curves and lateral (LAT) kilo-Voltage (kV) setup images. The planning CT image and the selected treatment fraction data are collected. If the changes in BHL relate to the displacement of various bones in the kV setup, images are assessed. Furthermore, the maximum heart distance inside the treatment field is compared from LAT MV portal images. The median and mean values of the BHL are nearly identical in different fractions (good reproducibility). However, the mean BHL values between planning and all measured fractions are statistically different; 16.3 vs. 20.8 mm for the planning and measured fractions (p < 0.001), which indicates that the variability of BHL is significantly different. While reproducibility testing shows good agreement for inter-fractional breath-hold level, the variability between planning and fractions is relatively poor.

Machine Learning to Predict the Quality of a Left-Sided Whole Breast Radiotherapy Treatment Plan

<h3>Purpose/Objective(s)</h3> Develop a Support Vector Machine (SVM) model that uses dosimetric data to predict the quality of a breast radiotherapy treatment plan. <h3>Materials/Methods</h3> One hundred twenty left-sided breast cancer patients from a single institute were included in the study. They were treated with 15-fractions whole breast radiotherapy up to 40.05 Gy with a concomitant boost to deliver 48 Gy to the tumor bed. There was no treatment of lymph nodes. Dose was delivered with a fixed-beam treatment mode and delivered plans were manually created. For each patient, a second treatment plan was generated, using an in-house system for automated plan generation. The treating clinician evaluated the two available plans for each patient and assigned a sentence regarding the quality of the plan in the format of yes/no variable (well optimized plan i.e., "yes" or plan that can be further optimized i.e., "no"). A quantitative scoring tool (ST) already used by Orecchia et al was used to assign 0, 0.5 or 1 points for each involved OAR and PTVs depending on both the fulfilment of multiple DVH constraints and on achieved coverage level for PTVs. Four SVM models were trained using 216 plans (arbitrarily selected from the available 240) using: i) dose volume parameters for target and OARs of each plan, ii) ST and iii) the clinician's plan sentence. Training was performed through iterative optimization using ten Cross-validation folds with four models: a) Model 1 with the ST only, b) Model 2 with the difference between dose volume parameters and the DVH constraints, c) Model 3 with both information from models 1 and 2 and d) Model 4 with ST and dose volume parameter. All models had clinician's sentence as response variable. Finally, the 24/240 patients not used for training were used for final validation. Models' performances were assessed through confusion matrix parameters and multiclass ROC analyses on the training and independent validation set. <h3>Results</h3> The involved clinician refereed as "yes" 92 plans (77%) out of 120 and "no" the remaining 28 in the manual set; 79 plans (66%) were judged "yes" and 41 "no" in the automatic set. Results in terms of Accuracy (ACC), Positive Predicted Values (PPV), True Positive Rates (TPR) and Area under Curve (AUC) for the four models are presented in table 1. <h3>Conclusion</h3> Clinicians' judgements are crucial in daily plan evaluations. We have proposed supervised learning to predict if a plan will be considered by clinician well optimized or not. Results are encouraging and the tool could potentially become useful for aiding treatment planners and reducing clinicians' workload.

PO-1216 Factors affecting cardiac dose in left-sided whole breast radiotherapy in a single institution

PO-1216 Factors affecting cardiac dose in left-sided whole breast radiotherapy in a single institution

Dose to the Left Anterior Descending Artery Correlates With Cardiac Events After Irradiation for Breast Cancer

Although global heart dose has been associated with late cardiac toxic effects in patients who received radiation therapy for breast cancer, data detailing the clinical significance of cardiac substructure dosimetry are limited. We investigated whether dose to the left anterior descending artery (LAD) correlates with adverse cardiac events. We identified 375 consecutively treated female patients from 2012 to 2018 who received left-sided breast or chest wall irradiation (with or without regional nodal irradiation). Medical records were queried to identify cardiac events after radiation therapy. Mean and maximum LAD and heart doses (LAD Dmean, LAD Dmax, heart Dmean, and heart Dmax) were calculated and converted to 2-Gy equivalent doses (EQD2). Univariate and multivariable Cox regression analyses were performed to determine association with cardiac toxic effects. Potential dose thresholds for each of the 4 dose parameters were identified by receiver operating characteristic (ROC) curve analysis, after which Kaplan-Meier analysis was performed to compare cardiac event-free survival based on these constraints. Median follow-up time was 48 months. Thirty-six patients experienced a cardiac event, and 23 patients experienced a major cardiac event. On univariate and multivariable analyses, increased LAD Dmean, LAD Dmax, and heart Dmean were associated with increased risk of any cardiac event and a major cardiac event. ROC curve analysis identified a threshold LAD Dmean EQD2 of 2.8 Gy (area under the ROC curve, 0.69), above which the risk for any cardiac event was higher (P=.001). Similar results were seen when stratifying by LAD Dmax EQD2 of 6.7 Gy (P=.005) and heart Dmean EQD2 of 0.8 Gy (P=.01). Dose to the LAD correlated with adverse cardiac events in this cohort. Contouring and minimizing dose to the LAD should be considered for patients receiving radiation therapy for left-sided breast cancer.

Deep Inspiration Breath Hold and Global Longitudinal Strain in Women Undergoing Left-Sided Breast Irradiation

Deep Inspiration Breath Hold and Global Longitudinal Strain in Women Undergoing Left-Sided Breast Irradiation

Evaluation of image-guided and surface-guided radiotherapy for breast cancer patients treated in deep inspiration breath-hold: A single institution experience.

Nowadays, deep inspiratory breath-hold is a common technique to reduce heart dose in left-sided breast radiotherapy. This study evaluates the evolution of the breath-hold technique in our institute, from portal imaging during dose delivery to continuous monitoring with surface-guided radiotherapy (SGRT). Setup data and portal imaging results were analyzed for 98 patients treated before 2014, and SGRT data for 228 patients treated between 2018 and 2020. For the pre-SGRT group, systematic and random setup errors were calculated for different correction protocols. Residual errors and reproducibility of breath-holds were evaluated for both groups. The benefit of using SGRT for initial positioning was evaluated for another cohort of 47 patients. Online correction reduced the population mean error from 3.9mm (no corrections) to 1.4mm. Despite online setup correction, deviationsgreater than3mm were observed in about 10% and 20% of the treatment beams in ventral-dorsal and cranial-caudal directions, respectively. However, these percentages were much smaller than with offline protocols or no corrections. Mean absolute differences between breath-holds within a fraction were smaller in the SGRT-group (1.69mm) than in the pre-SGRT-group (2.10mm), and further improved with addition of visual feedback (1.30mm). SGRT for positioning did not improve setup accuracy, but slightly reduced the time for imaging and setup correction, allowing completion within 3.5min for 95% of fractions. For accurate radiotherapy breast treatments using deep inspiration breath-hold, daily imaging and correction is required. SGRT provides accurate information on patient positioning during treatment and improves patient compliance with visual feedback.

Abstract PD5-02: Cardioprotective strategy for non-metastatic breast cancer patients receiving an anthracycline-based chemotherapy: subgroup analysis focused on impact of postoperative breast radiation therapy of the preplanned interim analysis of the phase 3 SAFE trial (NCT2236806)

Abstract Background: several studies have evaluated cardioprotective strategies to prevent myocardial dysfunction in patients receiving cardiotoxic therapies. However, the optimal approach still represents a controversial issue. The SAFE trial (ClinicaTrials.gov identifier: NCT2236806) is a four-arm, randomized, phase 3, double-blind, placebo-controlled study. The objective is to determine whether pharmacological cardioprevention could reduce subclinical heart damage in breast cancer patients treated with anthracycline-based chemotherapy. This is a subgroup analysis focused on the impact of postoperative breast radiation therapy (RT) of the recently published pre-specified interim analysis on the first 174 patients who had completed cardiac assessment at 12-month. Methods: patients were eligible for trial inclusion if they had indication to primary or postoperative systemic therapy using an anthracycline-based regimen. Patients with prior diagnosis of cardiovascular disease were excluded. Cardioprotective therapy (bisoprolol, ramipril, or both drugs, as compared to placebo) was administered for 1 year from the initiation of chemotherapy or until the end of trastuzumab therapy in case of HER2 positive patients. The primary endpoint was defined as detection of any subclinical impairment (worsening ≥10%) in myocardial function and deformation measured with standard and 3-dimensional (3D) echocardiography, left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS). Results: at 12-month, 3D-LVEF worsened by 4.4% in placebo arm and 3.0%, 1.9%, 1.3% in ramipril, bisoprolol, ramipril plus bisoprolol arms, respectively (P = .005). GLS worsened by 6.0% in placebo arm and 1.5%, .6% in ramipril, and bisoprolol arms, respectively; whereas it was unchanged (.1% improvement) in ramipril plus bisoprolol arm (P &amp;lt; .001). The percentage of patients showing a reduction ≥10% in 3D-LVEF was 19% in placebo arm, 11.5% in ramipril arm, 11.4% in bisoprolol arm and 6.8% in ramipril plus bisoprolol arm; 35.7% patients receiving placebo showed a ≥10% GLS worsening compared to 15.9% (ramipril), 13.6% (bisoprolol), and 13.6% (ramipril plus bisoprolol) (P = .025). Concerning differences in 3D-LVEF changes from baseline to end of treatment, bisoprolol-containing arms showed significant benefit in patients not receiving RT (P = .09), in patients receiving right-sided breast RT (P = .0001), and with lesser extent, in patients receiving left-sided RT (P = .041). No significant benefit was shown in ramipril-containing arms. Concerning differences in GLS changes from baseline to end of treatment, bisoprolol-containing arms showed significant benefit in patients not receiving RT (P = .0001) and in patients receiving right-sided breast RT (P = .0001), while no benefit was shown in patients receiving left-sided breast RT (P = .270). Ramipril-containing arms showed significant benefit in patients not receiving RT (P = .035) and in patients receiving left-sided breast RT (P = 0.14), while no benefit was shown in right-sided breast RT (P = .260). Conclusions: at the interim analysis, cardioprotective pharmacological strategies in patients affected by breast cancer receiving an anthracycline-based chemotherapy are well tolerated and seem to protect against cancer therapy-related LVEF decline and heart remodeling. This favorable effect seems to be reduced in patients receiving postoperative left-sided breast RT, thus calling for further investigations on potentially radiation-related early subclinical heart damage. Citation Format: Icro Meattini, Giuseppe Barletta, Carlotta Becherini, Luca Visani, Francesca Martella, Mario Airoldi, Domenico Amoroso, Luigi Coltelli, Chiara Bellini, Giulia Stocchi, Victoria Lorenzetti, Carolina Orsatti, Lucia Angelini, Lorenzo Livi. Cardioprotective strategy for non-metastatic breast cancer patients receiving an anthracycline-based chemotherapy: subgroup analysis focused on impact of postoperative breast radiation therapy of the preplanned interim analysis of the phase 3 SAFE trial (NCT2236806) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD5-02.

Heart-Sparing Capability and Positional Reproducibility of Continuous Positive Airway Pressure in Left-Sided Breast Radiation Therapy

PurposeOur purpose was to investigate the interfraction and intrafraction reproducibility and practical applicability of continuous positive airway pressure (CPAP) for left breast volumetric modulated arc therapy (VMAT). Methods and MaterialsInterfraction reproducibility of the position of the heart was evaluated by measuring the heart-to-target distance on 20 planning computed tomography (CT) and 300 daily cone beam CT of 20 patients with left breast cancer treated with a 15-fraction VMAT. The dosimetric metrics of the whole heart and its substructures were compared between CPAP and free-breathing based VMAT plans. Intrafraction reproducibility was evaluated by measuring the motions of the breast target and diaphragm in 4-dimensional CT of 20 female patients with nonbreast cancer. Lastly, we analyzed the CPAP compliance data of 237 consecutive patients with left-sided breast cancer with and without internal mammary node irradiation (IMNI). ResultsThe heart position was reproducible as evidenced by an absolute average heart-to-target distance error of 2.0 ± 2.0 mm. Compared with free-breathing, CPAP significantly reduced the mean heart dose and the dose to the left ventricle and left anterior descending artery. The average intrafraction position variation of the breast target was 0.5 ± 0.5, 2.5 ± 2.0, and 1.8 ± 1.4 mm in the mediolateral, craniocaudal, and anteroposterior directions, respectively. CPAP was successfully applied in 221 patients (93%), with a mean heart dose of 1.6 ± 0.7 Gy (IMNI: 2.0 Gy and no IMNI: 1.1 Gy). ConclusionsCPAP has adequate heart-sparing capability and sufficient reproducibility in VMAT for left-sided breast cancer treatment, with a high compliance rate. Thus, CPAP is applicable in routine practice for left-sided breast cancer radiation therapy.

Left-sided Breast Cancer Irradiation With Deep Inspiration Breath-hold: Changes in Heart and Lung Dose in Two Periods

Post-operative radiotherapy for breast cancer can increase cardiac disease in a dose-dependent manner. In this study we show the reduction of dose to heart and left anterior descending artery (LAD) which can be achieved by using "Deep inspiration breath-hold" (DIBH) technique.Tangential 3D-planned radiation was delivered to 357 patients with left-sided breast cancer, 159 of them with the DIBH technique. A distinction was made according to fractionation scheme.The mean heart dose was significantly reduced by DIBH from 2.64 Gy to 1.39 Gy (p<0.001). The mean dose to the LAD was significantly reduced from 5.68 Gy to 3.88 Gy (p<0.001). Mean dose and volume receiving 5, 10 and 15 Gy of ipsilateral lung were higher with both hypofractionated schedule and conventional fractionation in the DIBH group.DIBH in left-sided breast irradiation is an effective method of reducing the radiogenic heart dose.

OD54 - Bias-free comparison of VMAT and IMRT strategies for left-sided whole breast irradiation using automated planning

OD54 - Bias-free comparison of VMAT and IMRT strategies for left-sided whole breast irradiation using automated planning

P268 - SGRT tolerance table optimization through transit dosimetry in DIBH left-sided breast radiation therapy: a preliminary study

P268 - SGRT tolerance table optimization through transit dosimetry in DIBH left-sided breast radiation therapy: a preliminary study

Heart-Sparing Capability and Reproducibility of Continuous Positive Airway Pressure (CPAP) in Left-Sided Breast Radiation Therapy

<h3>Purpose/Objective(s)</h3> CPAP is a novel method to avoid heart radiation exposure during radiation therapy, recently proposed as an alternative to the current standard-of-care deep inspiration breath-hold technique. In this study, the heart dose, inter- and intrafraction motions in CPAP-based treatment were investigated. <h3>Materials/Methods</h3> A retrospective study on heart dose level and CPAP compliance included 237 left-sided breast cancer patients treated with CPAP-based VMAT in hypofractionation (with (n = 116) and without (n = 105) internal mammary node irradiation (IMNI)) between June 2020 and January 2021. During simulation, CT was obtained with free breathing (FB) and CPAP. For each treatment fraction, CBCT was acquired to confirm geometric accuracy within 3 mm tolerance. Two different datasets were used for reproducibility evaluations. Dataset 1: interfraction reproducibility was evaluated by measuring heart-to-PTV distance (MinHD), defined as the minimum distance between the line posteriorly tangential to the PTV and the heart, on 300 CBCT and 20 planning CT data of 20 women. Using dataset 1, heart-sparing effect was further explored by comparing dosimetric metrics of the whole heart and its substructures (e.g., atrium, ventricles, and vessels) between CPAP- and FB-based VMAT plans. Dataset 2: intrafraction reproducibility was evaluated in 20 women who were treated for different malignancies and underwent 4D CT with CPAP. <h3>Results</h3> Among 237 patients recruited, the CPAP compliance was 93% with a mean heart dose of 1.6 ± 0.7 Gy (no IMNI, 1.1 Gy; IMNI 2.0 Gy). The use of CPAP during treatment did not require additional time resource. The analysis of dataset 1 (i.e., total of 300 CBCT and 20 planning CT images) showed small variations of MinHD (0.6 ± 0.2 cm), demonstrating a reasonable agreement of the heart-to-PTV distance between the planning CT and CBCTs (MinHD difference < 0.2 cm, on average, for all patients). Compared with FB, the use of CPAP significantly reduced the mean heart dose (2.1 to 1.7 Gy), the mean dose to the left ventricle, the maximum dose to the left anterior descending artery, and the mean lung dose by 21%, 23%, 36%, and 23%, respectively. In dataset 2, the breast surface motion amplitude was 0.5 ± 0.5, 2.5 ± 2.0, and 1.8 ± 1.4 mm across the patients in the mediolateral, craniocaudal, and anteroposterior directions, respectively, and exceeded 5 mm for only two patients. <h3>Conclusion</h3> To the best of our knowledge, this is the first and largest study to evaluate the heart-sparing capability and reproducibility of CPAP-based VMAT for left-sided breast cancer treatment. A large population study confirmed a reasonably low irradiation to the heart with CPAP. This heart-sparing effect can be consistent across treatment fractions as demonstrated in sub-centimeter reproducibility of the heart position. For most of the women, the intrafraction breast motion with CPAP was minimal.

Impact of respiratory motion in dosimetric and clinical advantages for adjuvant left-sided breast radiotherapy.

We investigated the organ-sparing effect of the deep inspiration breath hold (DIBH) technique among different levels of lung expansion for left-side breast radiotherapy. This retrospective study enrolled 30 patients who received adjuvant left breast radiotherapy after breast-conserving surgery (BCS). Simulation scans of both DIBH and deep breathing four-dimensional computed tomography (4DCT) were acquired, and three treatment plans were generated for each patient. One plan was based on the DIBH images, and the other two plans were based on the mid-lung expansion (ME) and initial lung expansion (IE) phases retrieved from 4DCT data sets. Dosimetric comparisons and normal tissue complication probability (NTCP) models were conducted. We used image registration for displacement analysis and sought potential factors related to the dose benefit of DIBH. The DIBH plans resulted significantly lower doses to the heart, left ventricle (LV) and left anterior descending coronary artery (LAD), including the high- to low-dose areas, followed by the ME plans and IE plans (p < 0.05). DIBH reduced the risk of long-term cardiac mortality by 40% and radiation pneumonitis of the left lung by 37.96% compared with the IE plans (p < 0.001). The reduction in the mean dose to the heart and LV significantly correlated with anterior displacement of the left lung. The DIBH technique is a feasible tool to provide dosimetric and clinical advantages for adjuvant left-sided breast radiotherapy. Breathing pattern and the level of lung expansion seem to play an important role.

Assessment of visual feedback system for reproducibility of voluntary deep inspiration breath hold in left-sided breast radiotherapy

IntroductionDeep inspiration breath-hold (DIBH) for left-sided breast cancer radiotherapy reduces the dose exposure of the heart and left anterior descending coronary artery. DIBH requires the patient to maintain an adequate breath-hold position during their daily radiotherapy fraction. This study aimed to assess the reproducibility of the breath-hold position by implementing DIBH with visual feedback (VF) system. MethodsForty-three patients who underwent left-sided radiotherapy with DIBH were reviewed. Data from 35 patients who underwent DIBH with VF (VF-DIBH) were compared with data from 8 patients who underwent DIBH with audio coaching (AC-DIBH). Reproducibility during radiotherapy was evaluated using the portal images obtained. Images were acquired daily during the tangential field treatment with DIBH. The distances between the field edge and chest wall at the central beam axis were manually measured on the portal image and digital reconstruction radiograph (DRR). The displacements of the chest wall during radiotherapy were assessed by subtracting the measurement made on the portal image from the DRR measurement. The overall average distances for the VF-DIBH and AC-DIBH cohorts were compared to assess reproducibility. The statistical analysis was performed using Mann–Whitney U tests (p < 0.05). ResultsThe mean chest wall displacement (±2 SD) was 0.59 ± 3.64 mm for VF-DIBH and 2.09 ± 4.96 mm for AC-DIBH, respectively. This value differed significantly between the VF-DIBH and AC-DIBH cohorts (p < 0.001). ConclusionIn DIBH radiotherapy, the implementation of VF was confirmed to improve breath-hold position reproducibility, and the utility of VF for DIBH was demonstrated.

Clinical Dosimetric Comparison of Three Radiotherapy Techniques for Left-Sided Breast and Lymphatic Irradiation

Clinical Dosimetric Comparison of Three Radiotherapy Techniques for Left-Sided Breast and Lymphatic Irradiation