Cardiac dose-sparing effects of deep-inspiration breath-hold in left breast irradiation

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

Aim

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.

Materials and Methods

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.

Results

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.

Conclusion

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.

Dosimetric impact of different multileaf collimators on cardiac and left anterior descending coronary artery dose reduction

Introduction

Radiotherapy (RT) may increase the dose of heart structure like left anterior descending coronary artery (LAD). The purpose of this paper was to evaluate the impact of various multileaf collimators (MLCs) in shielding organ at risks (OARs), especially LAD, of patients with left breast cancer.

Materials and Methods

Forty-five patients with left breast cancer were selected. The treatment plans were created applying three techniques for all patients. In the first plan (uncovered LAD), the treatment plan was made without considering LAD as OARs. In the two other plans, two MLCs with different leaf widths (6.8 mm and 5 mm) were used to shield the LAD. For all plans, MLC was shielded as much of OAR as possible without compromising planning target volume (PTV) coverage. Dosimetric parameters of the heart, LAD, and ipsilateral lung were assessed.

Results

Compared to other plans, the covered LAD plan 1(CL1) obtained lower lung, cardiac, and LAD doses with the same PTV coverage. On average, the mean heart dose decreased from 6.2 Gy to 5.4 Gy by CL1, and the average mean dose to the LAD was reduced from 36.4 Gy to 33.7 Gy, which was statistically significant. The average lung volume receiving >20 Gy was significantly reduced from 24.6% to 23.4%. Moreover, the results show that covered LAD plan 2(CL2) is less useful for shielding OARs compared to CL1.

Conclusion

CL1 plans may reduce OAR dose for patients without compromising the target coverage. Hence, the proper implementation of MLC can decrease the side effects of RT.

Dosimetric Planning Comparison for Left-Sided Breast Cancer Radiotherapy: The Clinical Feasibility of Four-Dimensional-Computed Tomography-Based Treatment Planning Optimization

Background: Adjuvant whole-breast radiotherapy (RT) is a significant part of the standard of care treatment after breast cancer (BC) conserving surgery. Modern techniques including intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) have constituted to better target coverage and critical organs sparing. However, BC survivors are at risk of developing radiation-induced cardiac toxicity. Hence, deep-inspiration breath-hold (DIBH) techniques have been implemented at many centers to further reduce cardiac exposure but require compliance. 4D-CT robust optimization can account for heart intrafractional motion per breathing phase. The optimization has been explored in cardiac sparing of breast IMRT compared to DIBH in a small sample size but has not been evaluated in substructures sparing, nor in VMAT. To provide patients who are not compliant to breath-hold with an optimal treatment approach, various heart sparing techniques need to be evaluated for statistical significance and clinical feasibility.

Aim: This retrospective study aimed to provide an extensive dosimetric heart sparing comparison of free-breathing, 4D-CT-based treatment planning, including robust optimization with DIBH-based treatment planning. Combinations of forward and inverse IMRT and VMAT are also considered.

Methods: Fifteen early stage left-sided BC standard treatment plans were selected. Breast, lung, left anterior descending artery (LAD), left ventricle (LV), and the whole heart were contoured on each 4D-CT phase and DIBH CT dataset. Each treatment plan was optimized using forward/inverse IMRT and VMAT on the following CT datasets: DIBH, average 4D-CT, and the complete 4D-CT dataset needed for robust optimization. Dose-volume histograms were used to compare V_5GyHeart, mean heart dose, mean and max LAD dose, mean LV dose, and V_50%Lung.

Results: All RT techniques assessed including 4D robust optimization were clinically feasible. Statistically significant differences in mean heart, LAD and LV dose, max LAD dose, and V_5GyHeart (p < 0.01) but no difference in V_50%Lung (p = 0.29) were found between different techniques. IMRT DIBH achieved the optimal cardiac and substructure sparing among treatment plans. 4D robust IMRT had significantly greater mean heart and LV dose than DIBH IMRT (p ≤ 0.01), except LAD dose. Among free-breathing methods, no difference in all cardiac and substructure dose parameters was observed (p > 0.2) in comparing forward and inverse IMRT with average 4D-CT, inverse average 4D-CT, and 4D robust with IMRT, and between average 4D-CT VMAT and 4D robust VMAT. Only V_5GyHeart and mean LV dose were significantly greater in 4D robust VMAT (p < 0.01) compared to DIBH VMAT. Mean heart and LV doses were significantly reduced (p < 0.01) in DIBH IMRT compared to DIBH VMAT. Moreover, mean heart and LV dose, V_5GyHeart were significantly reduced in inverse IMRT average 4D-CT compared to average 4D-CT VMAT (p < 0.02) and in 4D robust IMRT compared to 4D robust VMAT (p < 0.04).

Conclusion: This study demonstrated the clinical feasibility of 4D robust optimization in limiting the cardiac and substructures dose during free-breathing RT with both IMRT/VMAT for patients who are not compliant with breath-hold RT. However, this study also presents that 4D robust optimization can reduce LAD dose but not fully outperform DIBH or conventional 4D-CT-based planning with IMRT/VMAT in heart sparing in treating early staged left-sided BC patients.

Comparison of Deep Inspiration Breath Hold Versus Free Breathing in Radiotherapy for Left Sided Breast Cancer

Objectives

Modern breast cancer techniques, such as the deep inspiration breath-hold (DIBH) technique has been applied for left-sided breast cancer. Whether the DIBH regimen is the optimal solution for left-sided breast cancer remains unclear. This meta-analysis aims to elucidate the differences of DIBH and free-breathing (FB) for patients receiving radiotherapy for left-sided breast cancer and provide a practical reference for clinical practice.

Methods

Relevant research available on PubMed, Embase, Cochrane Library, and the Web of Science published before November 30, 2021 was independently and systematically examined by two investigators. Data were extracted from eligible studies for assessing their qualities and calculating the standardized mean difference (SMD) and 95% confidence intervals (CIs) using Review Manager software 5.4 (RevMan 5.4).

Results

Forty-one studies with a total of 3599 left-sided breast cancer patients were included in the meta-analysis. Compared with FB, DIBH reduced heart dose (Dmean, Dmax, V30, V10, V5), left anterior descending branch (LAD) dose (Dmean, Dmax), ipsilateral lung dose (Dmean, V20, V10, V5), and heart volume significantly. Lung volume increased greatly, and a statistically significant difference. For contralateral breast mean dose, DIBH has no obvious advantage over FB. The funnel plot suggested this study has no significant publication bias.

Conclusions

Although DIBH has no obvious advantage over FB in contralateral breast mean dose, it can significantly reduce heart dose, LAD dose, ipsilateral lung dose, and heart volume. Conversely, it can remarkably increase the ipsilateral lung volume. This study suggests that soon DIBH could be more widely utilized in clinical practice because of its excellent dosimetric performance.

Comparison of organs at risk doses between deep inspiration breath-hold and free-breathing techniques during radiotherapy of left-sided breast cancer: A Meta-Analysis

After radiotherapy (RT) of left-sided breast cancer patients, organs at risk (OARs) such as heart, left anterior descending (LAD) coronary artery, and left lung could be affected by radiation dose in the long term. The objective of this study was to perform a comprehensive meta-analysis and determine OARs dose reduction during left-sided breast cancer treatment using different RT modalities combined with deep inspiration breath-hold (DIBH) relative to free-breathing (FB). PubMed, Scopus, EMBASE, ProQuest, Google Scholar, and Cochrane Library electronic databases were used to search for studies until June 6, 2021. Nineteen eligible studies were selected and analyzed using the RevMan 5.3 statistical software package. The pooled weighted mean difference (MD) with their 95% confidence intervals for each of the three OAR mean doses were determined using a random-effects meta-analysis model to assess the dose reductions. From a total of 189 studies, 1 prospective study, 15 retrospective studies, and 3 randomized control trials (RCTs) with an overall of 634 patients were included. Reduction of doses to the heart (weighted MD = -1.79 Gy; 95% CI (-2.28, -1.30); P = 0.00001), LAD (weighted MD = -8.34 Gy; 95% CI (-11.06, -5.61); P = 0.00001), and left-lung (weighted MD = -0.90 Gy; 95% CI (-1.19, -0.61); P = 0.00001) were observed using DIBH combinations relative to FB combination. This study emphasizes that during the treatment of left-sided breast/chest wall (CW) ± supraclavicular (SCV) ± infraclavicular (ICV) ± internal mammary chain (IMC) lymph nodes (LN) ± axillary (Ax)/ cancer patients, different RT modalities combined with DIBH techniques are better options to reduce dose to OARs compared to FB, which benefits to minimize the long-term complications.

The impact of modern radiotherapy on long-term cardiac sequelae in breast cancer survivor: a focus on deep inspiration breath-hold (DIBH) technique

INTRODUCTION

One of the most feared side effects of radiotherapy (RT) in the setting of breast cancer (BC) patients is cardiac toxicity. This side effect can jeopardize the quality of life (QoL) of long-term survivors. The impact of modern techniques of RT such as deep inspiration breath hold (DIBH) have dramatically changed this setting. We report and discuss the results of the literature overview of this paper.

MATERIALS AND METHODS

Literature references were obtained with a PubMed query, hand searching, and clinicaltrials.gov.

RESULTS

We reported and discussed the toxicity of RT and the improvements due to the modern techniques in the setting of BC patients.

CONCLUSIONS

BC patients often have a long life expectancy, thus the RT should aim at limiting toxicities and at the same time maintaining the same high cure rates. Further studies are needed to evaluate the risk-benefit ratio to identify patients at higher risk and to tailor the treatment choices.

The cardiac toxicity of radiotherapy - a review of characteristics, mechanisms, diagnosis, and prevention

PURPOSE

Radiation-induced heart disease (RIHD) is one of the most serious complications of radiotherapy. The purpose of this paper is to review recent researches about cardiac toxicity of radiotherapy in clinical characteristics, mechanisms, diagnosis, and prevention.

CONCLUSIONS

Powered by the rapid development of medicine, the overall survival (OS) of cancer has been improved significantly. Surgery, chemotherapy, and radiotherapy (RT) are three critical ways in the comprehensive treatments of cancer. There is a consensus that early diagnosis and interventions for the prevention of RIHD are crucial. This review concludes recent clinical and experimental studies on RIHD. RIHD, a heterogeneous and serious disease, is a spectrum of heart disease including myocardial disease, pericarditis, coronary artery disease, valvular heart disease, and conduction system dysfunction. Mean heart dose, biomarkers, and detecting techniques are important components in detecting heart injury. Improvements in radiotherapy regimens remain the primary goal of prevention. Further investigation is needed beyond the observation period of most of these studies.

Split-VMAT technique to control the deep inspiration breath hold time for breast cancer radiotherapy

BACKGROUND

To improve split-VMAT technique by optimizing treatment delivery time for deep-inspiration breath hold (DIBH) radiotherapy in left-sided breast cancer patients, when automatic beam-interruption devices are not available.

METHODS

Ten consecutive patients were treated with an eight partial arcs (8paVMAT) plan, standard of care in our center. A four partial arcs (4paVMAT) plan was also created and actual LINAC outputs were measured, to evaluate whether there was a dosimetric difference between both techniques and potential impact on the delivered dose. Subsequently, ten other patients were consecutively treated with a 4paVMAT plan to compare the actual treatment delivery time between both techniques. The prescribed dose was 40.05 Gy/15 fractions on the PTV breast (breast or thoracic wall), lymph nodes (LN) and intramammary lymph node chain (IMN). Treatment delivery time, PTVs coverage, conformity index (CI), organs at risk (OAR) dose, monitor units (MU), and gamma index were compared.

RESULTS

Both split-VMAT techniques resulted in similar dose coverage for the PTV Breast and LN, and similar CI. For PTV IMN we observed a 5% increased coverage for the volume receiving ≥ 36 Gy with 4paVMAT, with an identical volume receiving ≥ 32 Gy. There was no difference for the OAR sparing, with the exception of the contralateral organs: there was a 0.6 Gy decrease for contralateral breast mean (p ≤ 0.01) and 1% decrease for the volume of right lung receiving ≥ 5 Gy (p = 0.024). Overall, these results indicate a modest clinical benefit of using 4paVMAT in comparison to 8paVMAT. An increase in the number of MU per arc was observed for the 4paVMAT technique, as expected, while the total number of MU remained comparable for both techniques. All the plans were measured with the Delta4 phantom and passed the gamma index criteria with no significant differences. Finally, the main difference was seen for the treatment delivery time: there was a significant decrease from 8.9 to 5.4 min for the 4paVMAT plans (p < .05).

CONCLUSIONS

This study is mainly of interest for centers who are implementing the DIBH technique without automatic beam-holding devices and who therefore may require to manually switch the beam on and off during breast DIBH treatment. Split-VMAT technique with 4 partial arcs significantly reduces the treatment delivery time compared to 8 partial arcs, without compromising the target coverage and the OAR sparing. The technique decreases the number of breath holds per fraction, resulting in a shorter treatment session.

Volumetric arc therapy: A viable option for right-sided breast with comprehensive regional nodal irradiation in conjunction with deep inspiration breath hold

PURPOSE

Deep inspiration breath hold (DIBH) is an innovative technique routinely used for left-sided breast radiotherapy to significantly reduce harmful dose to the heart and ipsilateral lung. Currently, there is scant literature exploring DIBH for right-sided whole breast and regional nodal irradiation (WB & RNI). The purpose of this study is to examine if DIBH produces a clinically significant reduction in organ at risk (OAR) dose for right-sided WB + RNI, whilst comparatively analysing the use of volumetric arc therapy (VMAT) versus tangential inverse modulated radiotherapy (t-IMRT).

METHODS AND MATERIALS

Ten patients, previously treated for left sided breast cancer (with a FB and DIBH CT scan), were selected from our database to be retrospectively replanned to the right breast and nodal regions. Planning target volumes (PTV) were marked to include the whole right breast and regional nodes, encompassing the supraclavicular fossa (SCF) and internal mammary nodes (IMN). PTVs and OARs were contoured on the Pinnacle workstation according to the Radiation Therapy Oncology Group (RTOG) guidelines. VMAT and t-IMRT plans were generated to a prescribed dose of 50 Gy in 25 fractions on both the DIBH and FB data sets for dosimetric analysis.

RESULTS

Coverage of the right breast (mean, D95%) and SCF (D95%) were significantly improved with VMAT in comparison to t-IMRT, with no statistically significant variation on the IMN PTV (D95%). The use of DIBH did not impact PTV coverage compared with FB. VMAT reduced dose to the ipsilateral lung (mean, V20Gy), combined lungs (mean, V20Gy) and liver (D2cc); conversely dose to the heart (mean), left lung (mean, V5Gy) and contralateral breast (mean) were increased. For both techniques DIBH significantly improved dose to OARs including the ipsilateral lung (mean, V20Gy, V5Gy), total lung (mean, V20Gy), heart (mean, V25Gy) and liver (D2cc) when compared to FB.

CONCLUSION

DIBH could be considered for patients treated with right-sided WB and RNI due to a significant decrease in heart, ipsilateral lung, total lung and liver doses. VMAT significantly improves PTV coverage over t-IMRT whilst reducing dose to the ipsilateral lung and liver, albeit to the detriment of the left lung, contralateral breast and heart. The increase in heart dose can be mitigated by the use of DIBH. We recommend if VMAT is utilised for superior target volume coverage, DIBH should also be implemented to reduce OAR toxicity. RÉSUMÉ:   BUT: La retenue respiratoire profonde (DIBH) est une technique innovante couramment utilisée pour la radiothérapie du cÔté gauche du sein afin de réduire de manière significative la dose nocive pour le cŒur et le poumon ipsilatéral (13-15). Actuellement, il existe peu d'ouvrages sur la DIBH pour l'irradiation du sein entier du cÔté droit et des nodules régionaux (WB+RNI). L'objectif de cette étude est d'examiner si la DIBH produit une réduction cliniquement significative de la dose d'organe à risque (OAR) pour la WB+RNI du cÔté droit, tout en analysant comparativement l'utilisation de l'arcthérapie volumétrique (VMAT) par rapport à la radiothérapie par modulation d'intensité tangentielle (t-IMRT). MéTHODOLOGIE ET MATéRIEL: Dix scans tomodensitométriques avec un ensemble de données DIBH et de respiration libre (FB) ont été sélectionnés de manière rétrospective. Les volumes cibles de planification (PTV) ont été marqués pour inclure le sein droit entier et les ganglions régionaux, englobant la fosse supraclaviculaire (SCF) et les ganglions mammaires internes (IMN). Les PTV et les OAR ont été définis sur la station de travail Pinnacle conformément aux directives du groupe de radiothérapie oncologique (RTOG) (17). Les plans t-IMRT et VMAT ont été générés pour une dose prescrite de 50Gy en 25 fractions sur les ensembles de données DIBH et FB pour l'analyse dosimétrique. RéSULTATS: La couverture du sein droit (moyenne, D95%) et du SCF (D95%) a été significativement améliorée avec la VMAT par rapport à la t-IMRT, sans variation statistiquement significative sur la PTV IMN (D95%). L'utilisation de la DIBH n'a pas eu d'impact sur la couverture du PTV par rapport à la FB. La VMAT a réduit la dose dans le poumon ipsilatéral (moyenne, V20Gy), les poumons combinés (moyenne, V20Gy) et le foie (D2cc) ; à l'inverse, la dose dans le cŒur (moyenne), le poumon gauche (moyenne, V5Gy) et le sein controlatéral (moyenne) a été augmentée. Pour les deux techniques, la DIBH a amélioré de manière significative la dose aux OAR, y compris le poumon ipsilatéral (moyenne, V20Gy, V5Gy), le poumon total (moyenne, V20Gy), le cŒur (moyenne, V25Gy) et le foie (D2cc), par rapport à la respiration libre.

CONCLUSION

La DIBH pourrait être envisagé pour les patients traités par WB+RNI du cÔté droit en raison d'une diminution significative des doses dans le cŒur, le poumon ipsilatéral, le poumon total et le foie. La VMAT améliore considérablement la couverture de la PTV par rapport à la t-IMRT tout en réduisant la dose dans le poumon ipsilatéral et le foie, mais au détriment du poumon gauche, du sein controlatéral et du cŒur. L'augmentation de la dose au cŒur peut être atténuée par l'utilisation de la DIBH. Nous recommandons, si la VMAT est utilisée pour une couverture supérieure du volume cible, de mettre également en Œuvre la DIBH pour réduire la toxicité aux OAR.

Is prone free breathing better than supine deep inspiration breath-hold for left whole-breast radiotherapy? A dosimetric analysis

PURPOSE

The advantage of prone setup compared with supine for left-breast radiotherapy is controversial. We evaluate the dosimetric gain of prone setup and aim to identify predictors of the gain.

METHODS

Left-sided breast cancer patients who had dual computed tomography (CT) planning in prone free breathing (FB) and supine deep inspiration breath-hold (DiBH) were retrospectively identified. Radiation doses to heart, lungs, breasts, and tumor bed were evaluated using the recently developed mean absolute dose deviation (MADD). MADD measures how widely the dose delivered to a structure deviates from a reference dose specified for the structure. A penalty score was computed for every treatment plan as a weighted sum of the MADDs normalized to the breast prescribed dose. Changes in penalty scores when switching from supine to prone were assessed by paired t-tests and by the number of patients with a reduction of the penalty score (i.e., gain). Robust linear regression and fractional polynomials were used to correlate patients' characteristics and their respective penalty scores.

RESULTS

Among 116 patients identified with dual CT planning, the prone setup, compared with supine, was associated with a dosimetric gain in 72 (62.1%, 95% CI: 52.6-70.9%). The most significant predictors of a gain with the prone setup were the breast depth prone/supine ratio (>1.6), breast depth difference (>31 mm), prone breast depth (>77 mm), and breast volume (>282 mL).

CONCLUSION

Prone compared with supine DiBH was associated with a dosimetric gain in 62.1% of our left-sided breast cancer patients. High pendulousness and moderately large breast predicted for the gain.

Dosimetric Comparison of Intensity-Modulated Radiotherapy, Volumetric Modulated Arc Therapy and Hybrid Three-Dimensional Conformal Radiotherapy/Intensity-Modulated Radiotherapy Techniques for Right Breast Cancer

This study aimed to compare different types of right breast cancer radiotherapy planning techniques and to estimate the whole-body effective doses and the critical organ absorbed doses. The three planning techniques are intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT; two methods) and hybrid 3D-CRT/IMRT (three-dimensional conformal radiotherapy/intensity-modulated radiotherapy). The VMAT technique includes two methods to deliver a dose: non-continuous partial arc and continuous partial arc. A thermoluminescent dosimeter (TLD) is placed in the RANDO phantom to estimate the organ absorbed dose. Each planning technique applies 50.4 Gy prescription dose and treats critical organs, including the lung and heart. Dose-volume histogram was used to show the planning target volume (V95%), homogeneity index (HI), conformity index (CI), and other optimized indices. The estimation of whole-body effective dose was based on the International Commission on Radiation Protection (ICRP) Publication 60 and 103. The results were as follows: Continuous partial arc and non-continuous partial arc showed the best CI and HI. The heart absorbed doses in the continuous partial arc and hybrid 3D-CRT/IMRT were 0.07 ± 0.01% and 0% (V5% and V10%, respectively). The mean dose of the heart was lowest in hybrid 3D-CRT/IMRT (1.47 Gy ± 0.02). The dose in the left contralateral lung (V5%) was lowest in continuous partial arc (0%). The right ipsilateral lung average dose and V20% are lowest in continuous partial arc. Hybrid 3D-CRT/IMRT has the lowest mean dose to contralateral breast (organs at risk). The whole-body effective doses for ICRP-60 and ICRP-103 were highest in continuous partial arc (2.01 Sv ± 0.23 and 2.89 Sv ± 0.15, respectively). In conclusion, the use of VMAT with continuous arc has a lower risk of radiation pneumonia, while hybrid 3D-CRT/IMRT attain lower secondary malignancy risk and cardiovascular complications.

Effect of radiotherapy after breast-conserving surgery in elderly patients with early breast cancer according to the AJCC 8th Edition Breast Cancer Staging System in Japan

BACKGROUND

The number of elderly patients in Japan with breast cancer has been gradually increasing. The aim of this study was to determine the efficacy of radiotherapy (RT) after breast-conserving surgery (BCS) for elderly patients with early breast cancer who were restaged according to the 8th Edition Breast Cancer Staging System.

METHODS

We reviewed patients age ≥ 65 years who received BCS and adjuvant RT or BCS alone for breast cancer between 2010 and 2015 in our institution and restaged those patients using the AJCC 8th edition pathological prognostic staging system. We compared relapse-free survival (RFS) and overall survival (OS) rates in the RT group and no RT group.

RESULTS

A total of 170 patients were eligible for analysis: 94 (55.3%) were treated with RT and 76 (44.7%) were treated without RT. Age (p < 0.01) was associated with the use of RT. Adjuvant RT significantly improved RFS (95.75% vs 84.21%, p = 0.02). There was no significant difference between the OS rates in the two groups. Univariate analysis showed that pathologic T stage and N stage were significantly associated with both RFS and OS and that histologic grade, chemotherapy, HER2, and RT were significantly associated with RFS, but not with OS. RT reduced the risk of recurrence (HR = 0.56, 95% CI = 0.19-0.96, p = 0.04).

CONCLUSIONS

RT was associated with significantly improved RFS, but had no significant impact on OS in elderly patients with breast cancer after BCS. Adjuvant RT should be performed even for elderly patients with early breast cancer.

Matched-pair dosimetric comparison of cardiac radiation exposure between deep-inspiration breath-hold whole-breast radiation therapy with Active Breathing Coordinator and interstitial multicatheter high-dose-rate brachytherapy as accelerated partial breast irradiation in adjuvant treatment of left-sided breast cancer after breast-conserving surgery

BACKGROUND AND PURPOSE

To compare dosimetrically the radiation exposure to heart, left ventricle (LV), and left anterior descending artery (LAD) between whole-breast radiotherapy (WBRT) with Active Breathing Coordinator (ABC; ABC-WBRT) and interstitial multicatheter high-dose-rate (HDR) brachytherapy as accelerated partial breast irradiation (ABPI; imHDR-APBI) for left-sided breast cancer (BCA) after breast-conserving surgery (BCS).

MATERIALS AND METHODS

Between January 2016 and December 2019, 32 and 20 patients were treated with ABC-WBRT (63 Gy/2.25 Gy) and imHDR-APBI (32 Gy/4 Gy), respectively. Among them a matched-pair analysis was performed according to tumor location (clock position) before BCS as well as planning target volume of imHDR-APBI and boost volume of ABC-WBRT. This yielded 17 pairs of patients for whom dosimetric parameters for heart, LV, and LAD were evaluated. The Mann-Whitney test was used for comparison after adjusting for equivalent dose in 2‑Gy fractions (EQD2). In addition, a second analysis of ABC-WBRT to 40.05 Gy in 15 fractions was performed in order to account for the EQD2 difference between the 63-Gy ABC-WBRT and the imHDR-APBI protocol.

RESULTS

Tumor location for the 17 pairs of patients relative to breast quadrant was as follows: upper outer 8, lower outer 5, upper inner 3, and lower inner 1. There was no difference regarding mean heart dose (MHD) and V5, whereas D25%, D45%, V10, and V25 significantly favored imHDR-APBI. Likewise, mean dose- and V5-LV did not differ, while Dmax- and V23-LV were significantly higher for ABC-WBRT. For LAD, Dmax, D25%, and V30 significantly favored imHDR-APBI without differences for mean dose and V40. When comparing imHDR-APBI with the 40.05 Gy ABC-WBRT schedule, MHD and mean dose LV were significantly lower in favor of ABC-WBRT.

CONCLUSION

ABC-WBRT and imHDR-APBI yield similar low heart and LV exposure for left-sided BCA after BCS, whereas LAD can be better spared with imHDR-APBI.

A Retrospective Dosimetric Analysis of the New ESTRO-ACROP Target Volume Delineation Guidelines for Postmastectomy Volumetric Modulated Arc Therapy After Implant-Based Immediate Breast Reconstruction

Purpose: The European Society of Radiation & Oncology and Advisory Committee on Radiation Oncology Practice (ESTRO-ACROP) presented new guidelines for clinical target volume (CTV) delineation in post-mastectomy radiation therapy (PMRT) after implant-based immediate breast reconstruction (IBR-i). This study evaluated the dosimetric characteristics, dosimetric accuracy, and delivery accuracy of these guidelines in volumetric modulated arc therapy (VMAT). Methods and Materials: This retrospective study included 15 patients with left breast cancer who underwent mastectomy with tissue expander placement followed by PMRT. An experienced radiation oncologist delineated the CTV twice on the same image datasets based on the ESTRO-ACROP (EA-TVD) and conventional target volume delineation (C-TVD) guidelines. All VMAT plans, which used a double partial arc, were generated using six MV photons. Clinically relevant dose-volume parameters for organs at risk were compared. Dosimetric accuracy of the treatment plans and delivery accuracy were assessed. Results: Target volume of EA-TVD was significantly smaller than that of C-TVD. Although no statistically significant difference was noted in the target coverage between the two VMAT plans, EA-TVD VMAT significantly reduced the mean heart dose (3.99 ± 1.02 vs. 5.84 ± 1.78 Gy, p = 0.000), the maximum left anterior descending coronary artery (LAD) dose (9.43 ± 3.04 vs. 13.97 ± 6.04 Gy, p = 0.026), and the mean LAD dose (4.52 ± 1.31 vs. 6.35 ± 2.79 Gy, p = 0.028) compared with C-TVD VMAT. No significant difference was observed with respect to the total monitor units, plan complexity, and delivery quality assurance. Conclusions: This is the first study to show significant dose reduction for the normal heart and LAD tissue offered by the EA-TVD, while maintaining dosimetric and delivery accuracy, in PMRT after IBR-i in VMAT for left-sided breast cancer patients.

Postoperative radiotherapy with intensity-modulated radiation therapy versus 3-dimensional conformal radiotherapy in early breast cancer: A randomized clinical trial of KROG 15-03

PURPOSE

To investigate the safety and efficacy of intensity-modulated radiation therapy (IMRT) for early breast cancer compared with 3-dimensional conformal radiotherapy (3D-CRT) in a prospective and randomized trial.

METHODS AND MATERIALS

From March 2015 to February 2018, 693 patients with pT1-2N0M0 early breast cancer who underwent breast-conserving surgery were enrolled and randomly assigned into IMRT and 3D-CRT. The primary endpoint was 3-year locoregional recurrence-free survival (LRRFS). The secondary endpoints were recurrence-free survival, overall survival, acute toxicity, target coverage index, irradiation dose to organs at risk, and fatigue inventory. The radiation dose for the 3D-CRT arm was 59.4 Gy in 33 fractions for 6.5 weeks. It was 57.4 Gy in 28 fractions with simultaneous integrated boost for 5.5 weeks for the IMRT arm.

RESULTS

Of 693 patients, 349 and 344 patients received 3D-CRT and IMRT, respectively. There was no significant difference in LRRFS between the two arms. Conformity index of planning target volume was significantly superior in the IMRT arm than the 3D-CRT arm (p < 0.001). The mean lung dose and V₅-V₅₀ for the ipsilateral lung were significantly lower in the IMRT arm than the 3D-CRT arm (all p < 0.05). The incidence of grade 2 or higher dermatitis was significantly lower in the IMRT arm (p = 0.009).

CONCLUSION

Compared to 3D-CRT, IMRT showed similar results in locoregional tumor control but superior results in planning target volume coverage. When IMRT is used in breast cancer, the irradiation dose to an ipsilateral lung and skin toxicity can be reduced.

Predictors of cardiac and lung dose sparing in DIBH for left breast treatment

This retrospective study of left breast radiation therapy (RT) investigates the correlation between anatomical parameters and dose to heart or/and left lung in deep inspiration breath-hold (DIBH) compared to free-breathing (FB) technique. Anatomical parameters of sixty-seven patients, treated with a step-and-shoot technique to 50 Gy or 50.4 Gy were included. They consisted of the cardiac contact distances in axial (CCD_ax) and parasagittal (CCD_ps) planes, and the lateral heart-to-chest distance (HCD). Correlation analysis was performed to identify predictors for heart and lung dose sparing. Paired t-test and linear regression were used for data analysis with significance level of p = 0.05. All dose metrics for heart and lung were significantly reduced with DIBH, however 21% of patients analyzed had less than 1.0 Gy mean heart dose reduction. Both FB-CCD_psdistance and FB-HCD correlated with FB mean heart dose and mean DIBH heart dose reduction. The strongest correlation was observed for the ratio of FB-CCD_psand FB-HCD with heart dose sparing. A FB-CCD_ps and FB-HCD model was developed to predict DIBH induced mean heart dose reduction, with 1.04 Gy per unit of FB-CCD_ps/FB-HCD. Variation between predicted and actual mean heart dose reduction ranged from -0.6 Gy to 0.6 Gy. In this study, FB-CCD_ps and FB-HCD distance served as predictors for heart dose reduction with DIBH equally, with FB-CCD_ps/FB-HCD as a stronger predictor. These parameters and the prediction model could be further investigated for use as a tool to better select patients who will benefit from DIBH.

Left breast irradiation with tangential intensity modulated radiotherapy (t-IMRT) versus tangential volumetric modulated arc therapy (t-VMAT): trade-offs between secondary cancer induction risk and optimal target coverage

Background

Adjuvant radiotherapy is the standard treatment after breast-conserving surgery. According to meta-analyses, adjuvant 3d-conventional irradiation reduces the risk of local recurrence and thereby improves long-term survival by 5–10%. However, there is an unintended exposure of organs such as the heart, lungs and contralateral breast. Irradiation of the left breast has been related to long-term effects like increased rates of coronary events as well as second cancer induction. Modern radiotherapy techniques such as tangential intensity modulated radiotherapy (t-IMRT) and tangential volumetric modulated arc therapy (t-VMAT) and particularly deep inspiration breath hold (DIBH) technique have been developed in order to improve coverage of target volume and to reduce dose to normal tissue. The aim of this study was to compare t-IMRT-plans with t-VMAT-plans in DIBH position for left-sided breast irradiation in terms of normal tissue exposure, i.e. of lungs, heart, left anterior descending coronary artery (LADCA), as well as homogeneity (HI) and conformity index (CI) and excess absolute risk (EAR) for second cancer induction for organs at risk (OAR) after irradiation.

Methods

Twenty patients, diagnosed with left-sided breast cancer and treated with breast-preserving surgery, were included in this planning study. For each patient DIBH-t-IMRT plan using 5 to 7 beams and t-VMAT plan using four rotations were generated to achieve 95% dose coverage to 95% of the volume. Data were evaluated on the basis of dose-volume histograms: Cardiac dose and LADCA (mean and maximum dose, D25% and D45%), dose to ipsilateral and contralateral lung (mean, D20%, D30%), dose to contralateral breast (mean dose), total monitor units, V5% of total body and normal tissue integral dose (NTID). In addition, homogeneity index and conformity index, as well as the excess absolute risk (EAR) to estimate the risk of second malignancy were calculated.

Results

T-IMRT showed a significant reduction in mean cardiac dose of 26% (p = 0.002) compared to t-VMAT, as well as a significant reduction in the mean dose to LADCA of 20% (p = 0.03). Following t-IMRT, mean dose to the left lung was increased by 5% (p = 0.006), whereas no significant difference was found in the mean dose to the right lung and contralateral breast between the two procedures. Monitor units were 31% (p = 0.000004) lower for t-IMRT than for t-VMAT. T-IMRT technique significantly reduced normal tissue integral dose (NTID) by 19% (p = 0.000005) and the V5% of total body by 24% (p = 0.0007). In contrast, t-VMAT improved CI and HI by 2% (p = 0.001) and 0.4% (p = 0.00001), respectively. EAR with t-IMRT was significantly lower, especially for contralateral lung and contralateral breast (2–5/10,000 person years) but not for ipsilateral lung.

Conclusion

Compared to t-VMAT, t-IMRT in left-sided breast irradiation significantly reduced dose to organs at risk as well as normal tissue integral dose, and V5% total body. EAR with t-IMRT was significantly lower for contralateral lung and contralateral breast. T-VMAT, however, achieved better homogeneity and conformity. This may be relevant in individual cases where sufficient coverage of medial lymphatic target volumes is warranted.

Dosimetric analysis of tangent-based volumetric modulated arc therapy with deep inspiration breath-hold technique for left breast cancer patients

Background

Tangent-based intensity modulated radiation therapy (TIMRT) is a common adjuvant radiotherapy strategy for breast cancer patients. This study compared the dosimetric characteristics of tangent-based volumetric modulated arc therapy (TVMAT) and TIMRT for left breast cancer patients during deep inspiration breath-hold (DIBH) and free breathing (FB) techniques.

Methods

Fourteen patients with left breast cancer after breast-conserving surgery were included. The first arc started at 331.8–353.6 degrees and stopped at 281.8–315.0 degrees. The third arc started at 123.2–149.1 degrees and stopped at 88.0–96.0 degrees. The second and fourth arcs were reverse arcs of first and third arcs. DIBH-TIMRT inversing plans were generated using opposing tangential fields. Wilcoxon signed rank test and Spearman correlation were used to examine the significance of dose difference.

Results

Compared with FB-TVMAT, the mean heart dose of DIBH-TVMAT plans was reduced from 7.9 Gy to 3.2 Gy (p < 0.001). The average left lung volume receiving 30 Gy or more (V30Gy) was reduced from 12.9 to 5.7% (p < 0.001). DIBH-TVAMT plans resulted in a lower mean dose to the contralateral breast and lung (2 Gy and 0.7 Gy vs 3.4 Gy and 1.5 Gy, respectively) as compared to FB-TVMAT plans. Compared with DIBH-TIMRT, the average left lung V30Gy of DIBH-TVMAT plans was reduced from 8.5 to 5.7% (p = 0.031). As for low-dose areas, exposure of the left lung, right breast, heart and right lung volume with 10 Gy or more was not significantly different between the IMRT- and VMAT-plans.

Conclusions

DIBH-TVMAT for left breast cancer treatment retains treatment plan quality similar to the DIBH-IMRT technique without compromising dose restrictions to the heart, right breast and right lung. DIBH-TVMAT increased left lung protection but still had higher V5Gy to right breast and substantially higher V5Gy to heart. For left breast cancer patients receiving treatment with the DIBH technique, DIBH-TVMAT provides better treatment quality and is a safe and feasible treatment strategy.

Heart toxicity from breast cancer radiotherapy : Current findings, assessment, and prevention

Background

Late cardiac toxicities caused by (particularly left-sided) breast radiotherapy (RT) are now recognized as rare but relevant sequelae, which has prompted research on risk structure identification and definition of threshold doses to heart subvolumes. The aim of the present review was to critically discuss the clinical evidence on late cardiac reactions based on dose-dependent outcome reports for mean heart doses as well as doses to cardiac substructures.

Methods

A literature review was performed to examine clinical evidence on radiation-induced heart toxicities. Mean heart doses and doses to cardiac substructures were focused upon based on dose-dependent outcome reports. Furthermore, an overview of radiation techniques for heart protection is given and non-radiotherapeutic aspects of cardiotoxicity in the multimodal setting of breast cancer treatment are discussed.

Results

Based on available findings, the DEGRO breast cancer expert panel recommends the following constraints: mean heart dose <2.5 Gy; D_meanLV (mean dose left ventricle) < 3 Gy; V5_LV (volume of LV receiving ≥5 Gy) < 17%; V23_LV (volume of LV receiving ≥23 Gy) < 5%; D_meanLAD (mean dose left descending artery) < 10 Gy; V30_LAD (volume of LAD receiving ≥30 Gy) < 2%; V40_LAD (volume of LAD receiving ≥40 Gy) < 1%.

Conclusion

In addition to mean heart dose, breast cancer RT treatment planning should also include constraints for cardiac subvolumes such as LV and LAD. The given constraints serve as a clinicians’ aid for ensuring adequate heart protection. The individual decision between sufficient protection of cardiac structures versus optimal target volume coverage remains in the physician’s hand. The risk of breast cancer-specific mortality and a patient’s cardiac risk factors must be individually weighed up against the risk of radiation-induced cardiotoxicity.

A comparison of conventional and dynamic radiotherapy planning techniques for early-stage breast cancer utilizing deep inspiration breath-hold

BACKGROUND

For breast cancer patients, radiotherapy increases the risk of cardiac disease. Conventional three-dimensional conformal radiotherapy (3D-CRT) in deep inspiration breath-hold (DIBH) has demonstrated substantial reduction in cardiac doses as compared to treatment in free breathing. The purpose of this treatment planning study is to investigate if dynamic techniques in combination with DIBH could improve the quality of the treatment plans and further reduce the doses to the heart and other organs at risk for early-stage breast cancer patients.

MATERIAL AND METHODS

CT series in DIBH of 16 patients from a previous study were used. For each patient, treatment plans were generated with the following three techniques: 3D-CRT, tangential intensity-modulated radiotherapy (tIMRT) and volumetric modulated arc therapy with partial arcs (pVMAT). The treatment planning was performed focusing on planning target volume (PTV) coverage, V_95% >95%. Dose-volume histograms were calculated and compared. Doses to the heart, left anterior descending (LAD) coronary artery, ipsilateral and contralateral lung as well as the contralateral breast (CB) were assessed.

RESULTS

All plans fulfilled the criterion on PTV coverage. Compared to 3D-CRT, the dynamic plans obtained better dose homogeneity and conformity. The mean heart dose was similar for 3D-CRT and tIMRT, 1.3 and 1.1 Gy, respectively, but significantly higher for pVMAT, 1.6 Gy. The median V_25 Gy to the heart was 0% for all techniques. The LAD doses were generally lower with the dynamic techniques. The mean doses to the ipsi- and contralateral lung and CB were similar with tIMRT and 3D-CRT but significantly higher with pVMAT. V_20 Gy to the ipsilateral lung was significantly lower with tIMRT compared to 3D-CRT.

CONCLUSION

tIMRT and 3D-CRT with DIBH are better techniques for sparing heart tissue and other organs at risk without compromising target coverage in early-stage breast cancer irradiation compared to VMAT.

Heart-sparing volumetric modulated arc therapy for whole lung irradiation

PURPOSE

Whole lung irradiation (WLI) is indicated for subgroups of patients with lung metastases from Wilms' tumor (nephroblastoma). WLI has traditionally been performed with an anterior/posterior field arrangement with poor potential for heart sparing; thus, new techniques are desirable to achieve a lower dose to the heart.

MATERIALS AND METHODS

We utilized volumetric modulated arc therapy (VMAT) for WLI with 18 Gy in a patient with metastatic nephroblastoma. The planning results were compared against a three-dimensional (3D) conformal plan.

RESULTS

VMAT resulted in adequate target volume coverage with the prescribed dose. Mean heart dose was 10.2 Gy. The dose to organs at risk (OAR) was generally more favorable with VMAT when compared with a 3D-conformal radiotherapy plan.

DISCUSSION

WLI with VMAT provides superior sparing of OARs and especially a considerably lower dose to the heart.

Cardiovascular effects of radiation therapy

Radiation therapy (RT) plays a prominent role in the treatment of many cancers. With increasing use of RT and high overall survival rates, the risks associated with RT must be carefully considered. Of these risks, the cardiovascular and autonomic toxicities have been of significant concern. In fact, cardiovascular disease is the leading cause of nonmalignancy-related death in cancer survivors. The manifestations of radiation induced cardiac injury include the acute toxicities of myopericarditis and late toxicities including constrictive pericarditis, restrictive cardiomyopathy, coronary artery disease, valvular heart disease, heart failure, and conduction abnormalities. Neck and cranial RT have also been associated with significant long-term toxicities including accelerated occlusive carotid artery disease, autonomic dysfunction due to baroreceptor damage, and development of metabolic syndromes due to damage to the hypothalamic-pituitary axis. The clinical manifestations of radiation induced disease may not present until several years following the delivery of radiation. We review the adverse effects of RT on these organ systems and discuss risk reduction strategies that may effectively mitigate some of these adverse outcomes.