Treatment Of Left-sided Breast Cancer Research Articles

Deep inspiratory breath-hold radiotherapy on a Helical Tomotherapy unit: Workflow and early outcomes in patients with left-sided breast cancer

IntroductionThe clinical implementation of deep inspiratory breath-hold (DIBH) radiotherapy to reduce cardiac exposure in patients with left-sided breast cancer is challenging with helical tomotherapy(HT) and has received little attention. We describe our novel approach to DIBH irradiation in HT using a specially designed frame and manual gating, and compare cardiac substructure doses with the free-breathing (FB) technique. Material and methodsThe workflow incorporates staggered junctions and a frame that provides tactile feedback to the patient and monitoring for manual cut-off. The treatment parameters and clinical outcome of 20 patients with left-sided breast cancer who have undergone DIBH radiotherapy as a part of an ongoing prospective registry are reported. All patients underwent CT scans in Free Breathing (FB) and DIBH using the in-house Respiframe, which incorporates a tactile feedback-based system with an indicator pencil. Plans compared target coverage, cardiac doses, synchronizing treatment with breath-hold and avoiding junction repetition. MVCT scans are used for patient alignment. ResultsThe mean dose (Dmean) to the heart was reduced by an average of 34 % in DIBH-HT compared to FB-HT plans (3.8 Gy vs 5.7 Gy). Similarly, 32 % and 67.8 % dose reduction were noted in the maximum dose (D0.02 cc) of the left anterior descending artery, mean 12.3 Gy vs 18.1 Gy, and mean left ventricle V5Gy 13.2 % vs 41.1 %, respectively. The mean treatment duration was 451.5 sec with a median 8 breath-holds; 3 % junction locations between successive breath-holds were replicated. No locoregional or distant recurrences were observed in the 9-month median follow-up. ConclusionOur workflow for DIBH with Helical-Tomotherapy addresses patient safety, treatment precision and challenges specific to this treatment unit. The workflow prevents junction issues by varying daily breath-hold durations and avoiding junction locations, providing a practical solution for left-sided breast cancer treatment with HT.

Dosimetric effect of rotational setup errors in volumetric modulated arc therapy and field-in-field treatment of left-sided breast cancer

Setup errors are an important factor in the dosimetric accuracy of radiotherapy delivery. In this study, we investigated how rotational setup errors influence the dose distribution in volumetric modulated arc therapy (VMAT) and tangential field-in-field (FiF) treatment of left-sided breast cancer with supraclavicular lymph node involvement in deep inspiration breath hold. Treatment planning computed tomography images and radiotherapy plans of 20 patients were collected retrospectively for the study. Rotational setup errors up to 3° were simulated by rotating the planning images, and the resulting dosimetric changes were calculated. With rotational setup errors up to 3°, the median decrease of V95% to clinical target volume was less than 0.8 percentage point in both VMAT and FiF plans. The dose distribution of the heart and left anterior descending artery was more stable with respect to rotations in VMAT plans compared to FiF plans. Correction of ≥1° setup errors is recommended due to increased doses to the heart and left anterior descending artery after 1° setup errors.

Cardiorespiratory dose comparison among six radiotherapy regimens for patients with left-sided breast cancer

There is uncertainty regarding the benefits and drawbacks of various radiation protocols for the treatment of left-sided breast cancer. To address this issue, we conducted a Bayesian network analysis. First, we searched several electronic databases for eligible literature. Next, we pooled the data from twelve studies concerning three-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT), combined with either deep inspiratory breath-holding (DIBH) or free-breathing (FB) modalities. The integrated cardiac and pulmonary dosimetric indexes for all included treatments were compared using Bayesian networks. A direct meta-analysis indicated that for the two methods of 3D-CRT and IMRT, DIBH technology was more effective than FB in reducing the radiation dose to the heart and lungs. Additionally, according to the network results, DIBH was superior to FB in all six treatment options, regardless of whether the plan was 3D-CRT, IMRT, or VMAT. Besides, the combined data indicated that the FB-3D-CRT regimen had the weakest dosimetric advantage of all the treatments. Excluding FB-3D-CRT, each of the other five treatments had its own specific benefits. This is the first Bayesian study of several radiotherapy regimens for breast cancer patients on the left side, and the findings can be used to select appropriate radiotherapy programs for breast cancer patients.

Stability and reproducibility comparisons between deep inspiration breath-hold techniques for left-sided breast cancer patients: A prospective study.

Deep inspiration breath-hold (DIBH) is crucial in reducing the lung and cardiac dose for treatment of left-sided breast cancer. We compared the stability and reproducibility of two DIBH techniques: Active Breathing Coordinator (ABC) and VisionRT (VRT). We examined intra- and inter-fraction positional variation of the left lung. Eight left-sided breast cancer patients were monitored with electronic portal imaging during breath-hold (BH) at every fraction. For each patient, half of the fractions were treated using ABC and the other half with VRT, with an equal amount starting with either ABC or VRT. The lung in each portal image was delineated, and the variation of its area was evaluated. Intrafraction stability was evaluated as the mean coefficient of variation (CV) of the lung area for the supraclavicular (SCV) and left lateral (LLat) field over the course of treatment. Reproducibility was the CV for the first image of each fraction. Daily session time and total imaging monitor units (MU) used in patient positioning were recorded. The mean intrafraction stability across all patients for the LLat field was 1.3±0.7% and 1.5±0.9% for VRT and ABC, respectively. Similarly, this was 1.5±0.7% and 1.6±0.8% for VRT and ABC, respectively, for the SCV field. The mean interfraction reproducibility for the LLat field was 11.0±3.4% and 14.9±6.0% for VRT and ABC, respectively. Similarly, this was 13.0±2.5% and 14.8±9% for VRT and ABC, respectively, for the SCV. No difference was observed in the number of verification images required for either technique. The stability and reproducibility were found to be comparable between ABC and VRT. ABC can have larger interfractional variation with less feedback to the treating therapist compared to VRT as shown in the increase in geometric misses at the matchline.

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

Abstract 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.

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.

Comparison of normal tissue doses in deep inspiration breath-hold and free breathing methods for radiotherapy of left-sided breast cancer using 4D-XCAT digital phantom.

To evaluate normal lung and heart tissue doses for treatment of left-sided breast cancer in deep inspiration breath-hold (DIBH) and free breathing (FB) as a function of breast size and diaphragm displacement using 4D-XCAT digital phantom in a simulation study. 4D-XCAT digital phantom was used to create 36 left-sided breast cancer digital phantom datasets with different breast height (BH) of 40, 50, and 60 mm, breast length (BL) of 16, 17, and 18 mm, and diaphragm excursion of 20, 25, 30, and 35 mm. For each dataset, DIBH and FB treatment plans were prepared using planning computerized radiotherapy-three dimensional (PCRT-3D) treatment planning system (TPS) with superposition computational algorithm. Dose differences in DIBH and FB plans were assessed in terms of mean lung dose (MLD), the lung volume receiving ≤20 Gy (V20), normal tissue complication probability (NTCP) of the lung, mean heart dose (MHD), and the heart volume receiving ≤30 (V30). DIBH reduced mean dose and V20 and NTCP of the lung in all cases, by up to 4.37 Gy, 7.62%, and 18.95%. Mean dose and V30 of the heart were also significantly reduced by 5.02 Gy and 8.23%. The use of DIBH for left-sided breast cancer radiotherapy offers excellent possibilities for sparing critical normal tissue without compromising radiation dose to the target.

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.

Deep inspiration breath-hold for patients with left-sided breast cancer - A one-fits-all approach? A prospective analysis of patient selection using dosimetrical and practical aspects.

To prospectively analyze the feasibility of an algorithm for patient preparation, treatment planning, and selection for deep inspiration breath-hold (DIBH) treatment of left-sided breast cancer. From February 2017 to July 2019, 135 patients with left-sided breast cancer were selected and prepared for radiotherapy in DIBH. 99 received radiotherapy for the breast alone and 36 for the breast including the lymphatic drainage (RNI). Treatment plans DIBH and free breathing (FB) were calculated. Dosimetrical analyses were performed, and criteria were defined to assess whether a patient would dosimetrically profit from DIBH. Of the 135 patients, 97 received a DIBH planning CT and 72 were selected for treatment in DIBH according to predefined criteria. When using DIBH, there was a mean reduction of the DmeanHeart of 2.8 Gy and DmeanLAD of 4.2 Gy. seven patients did not benefit from DIBH regarding DmeanHeart, 23 regarding DmeanLAD. For the left lung, the V20Gy was reduced by 4.9%, the V30Gy by 2.7% with 15 and 29 patients not benefiting from DIBH, respectively. In the 25 patients treated in FB, the benefit of DIBH would have been lower than for patients treated with DIBH (ΔDmeanHeart0.7 Gy vs 3.4 Gy). Dosimetrically, DIBH is no "one-fits-all" approach. However, there is a statistically significant benefit when looking at a larger patient population. DIBH should be used for treatment of left-sided breast cancer in patients fit for DIBH. This analysis offers a well-designed dosimetrical analysis in patients treated with DIBH radiotherapy in an "every day" cohort.

Assessment of a conventional volumetric-modulated arc therapy knowledge-based planning model applied to the new Halcyon© O-ring linac in locoregional breast cancer radiotherapy.

The aim of this study was to evaluate the performance of a knowledge-based planning (KBP) model for breast cancer trained on plans performed on a conventional linac with 6 MV FF (flattening filter) beams and volumetric-modulated arc therapy (VMAT) for plans performed on the new jawless Halcyon© system with 6 MV FFF (flattening filter-free) beams. Based on the RapidPlan© (RP) KBP optimization engine, a DVH Estimation Model was first trained using 56 VMAT left-sided breast cancer treatment plans performed on a conventional linac, and validated on another 20 similar cases (without manual intervention). To determine the capacity of the model for Halcyon©, an additional cohort of 20 left-sided breast cancer plans was generated with RP and analyzed for both TrueBeam© and Halcyon© machines. Plan qualities between manual vs RP (followed by manual intervention) Halcyon© plans set were compared qualitatively by blinded review by radiation oncologists for 10 new independent plans. Halcyon© plans generated with the VMAT model trained with conventional linac plans showed comparable target dose distribution compared to TrueBeam© plans. Organ sparingwas comparable between the 2 devices with a slight decrease in heart dose for Halcyon© plans. Nine out of ten automatically generated Halcyon© plans were preferentially chosen by the radiation oncologists over the manually generated Halcyon© plans. A VMAT KBP model driven by plans performed on a conventional linac with 6 MV FF beams provides high quality plans performed with 6 MV FFF beams on the new Halcyon© linac.

A Comparative Dosimetric Study for the Treatment of Left-Sided Breast Cancer using Three-Dimensional Conformal Deep Inspiration Breath-Hold and Free-Breathing Intensity-Modulated Radiotherapy Techniques

Introduction: Most women with left-sided breast cancer are at an increased risk of heartmorbidity and mortality from the adjuvant radiotherapy due to an increase in heart absorbed dose during radiotherapy treatment. This study aimed to compare free-breathing intensity-modulated radiotherapy (FB-IMRT) and three-dimensional conformal deep inspiration breath-hold (3DCRT-DIBH) techniques in terms of the cardiac dose. Material and Methods: In total, 15 women with left-sided breast cancer underwent FB and DIBH computed tomography (CT) scans in the same supine position. For DIBH CT, 3D-CRT plans were created using two opposing wedged tangential fields and for FB-CT, 4-5 IMRT optimized tangential fields were created. All plans were evaluated using the dose-volume histogram. The data were analyzed in SPSS software version 20 (IBM, IL). Results: The FB-IMRT plans were more homogeneous and had more dose coverage and fewer hotspots, than the 3DCRT-DIBH plans; however, the planning target volume V95% was clinically acceptable for both techniques. Furthermore, the 3DCRT-DIBH plans were much faster and require fewer monitor units. A significantly lower mean dose of heart, left lung, left anterior descending coronary artery, right lung, and V10% left lung were observed in 3DCRT-DIBH plans, compared to FB-IMRT plans. Moreover, FB-IMRT plans showed a significant further dose reduction in heart V25% and V30%. Conclusion: The majority of the patients with left-sided breast cancer who treated with the DIBH technique were getting sufficient benefits of radiotherapy, and DIBH was a comprehensive strategy for reducing cardiac doses during radiotherapy treatment.

Dosimetric and Radiobiological Comparison of Five Techniques for Postmastectomy Radiotherapy with Simultaneous Integrated Boost.

Purpose To compare five techniques for the postmastectomy radiotherapy (PMRT) with simultaneous integrated boost (SIB). Materials and Methods Twenty patients with left-sided breast cancer were retrospectively selected. Five treatment plans were created for each patient: TomoDirect (TD), unblocked helical TomoTherapy (unb-HT), blocked HT (b-HT), hybrid intensity-modulated radiotherapy (hy-IMRT), and fixed-field IMRT (ff-IMRT). A dose of 50.4 Gy in 28 fractions to PTVtotal and 60.2 Gy in 28 fractions to PTVboost were prescribed. The dosimetric parameters for targets and organs at risk (OARs), the normal tissue complication probability (NTCP), the second cancer complication probability (SCCP) for OARs, and the treatment efficiency were assessed and compared. Results TD plans and hy-IMRT plans had similar good dose coverage and homogeneity for both PTVboost and PTVtotal and superior dose sparing for the lungs and heart. The ff-IMRT plans had similar dosimetric results for the target volumes compared with the TD and hy-IMRT plans, but gave a relatively higher NTCP and SCCP for the lungs. The unb-HT plans exhibited the highest OAR mean dose, highest NTCP for the lungs (0.97 ± 1.25‰) and heart (4.58 ± 3.62%), and highest SCCP for the lungs (3.57 ± 0.05%) and contralateral breast (2.75 ± 0.29%) among all techniques. The b-HT plans significantly outperformed unb-HT plans with respect to the sparing of the lungs and heart. This technique also showed the best conformity index (0.73 ± 0.08) for PTVboost and the optimal NTCP for the lungs (0.03 ± 0.03‰) and heart (0.61 ± 0.73%). Concerning the delivery efficiency, the hy-IMRT and ff-IMRT achieved much higher delivery efficiency compared with TomoTherapy plans. Conclusion Of the five techniques studied, TD and hy-IMRT are considered the preferable options for PMRT with SIB for left-sided breast cancer treatment and can be routinely applied in clinical practice.

Radiobiological comparison of 3D conformal and intensity modulated radiation therapy in the treatment of left-sided breast cancer

Radiobiological comparison of 3D conformal and intensity modulated radiation therapy in the treatment of left-sided breast cancer

Deep inspiration breath-hold for left-sided breast irradiation: Analysis of dose-mass histograms and the impact of lung expansion

BackgroundThe aim of this study was to compare dose-volume histogram (DVH) with dose-mass histogram (DMH) parameters for treatment of left-sided breast cancer in deep inspiration breath-hold (DIBH) and free breathing (FB). Additionally, lung expansion and anatomical factors were analyzed and correlated to dose differences.MethodsFor 31 patients 3D conformal radiation therapy plans were retrospectively calculated on FB and DIBH CTs in the treatment planning system. The calculated doses, structures and CT data were transferred into MATLAB and DVHs and DMHs were calculated. Mean doses (Dmean), volumes and masses receiving certain doses (Vx, Mx) were determined for the left lung and the heart. Additionally, expansion of the left lung was evaluated using deformable image registration. Differences in DVH and DMH dose parameters between FB and DIBH were statistically analyzed and correlated to lung expansion and anatomical factors.ResultsDIBH reduced Dmean (DVH) and relative V20 (V20 [%]) of the left lung in all patients, on average by − 19 ± 9% (mean ± standard deviation) and − 24 ± 10%. Dmean (DMH) and M20 [%] were also significantly reduced (− 12 ± 11%, − 16 ± 13%), however 4 patients had higher DMH values in DIBH than in FB. Linear regression showed good correlations between DVH and DMH parameters, e.g. a dosimetric benefit smaller than 8.4% for Dmean (DVH) in DIBH indicated more irradiated lung mass in DIBH than in FB. The mean expansion of the left lung between FB and DIBH was 1.5 ± 2.4 mm (left), 16.0 ± 4.0 mm (anterior) and 12.2 ± 4.6 mm (caudal). No significant correlations were found between expansions and differences in Dmean for the left lung. The heart dose in DIBH was reduced in all patients by 53% (Dmean) and this dosimetric benefit correlated to lung expansion in anterior.ConclusionsTreatment of left-sided breast cancer in DIBH reduced dose to the heart and in most cases the lung dose, relative irradiated lung volume and lung mass. A mass related dosimetric benefit in DIBH can be achieved as long as the volume related benefit is about ≥8–9%. The lung expansion (breathing pattern) showed no impact on lung dose, but on heart dose. A stronger chest breathing (anterior expansion) for DIBH seems to be more beneficial than abdominal breathing.

EP-1306 Gated treatment of left-sided breast cancer: evaluation of lung movement, irradiated volume and mass

EP-1306 Gated treatment of left-sided breast cancer: evaluation of lung movement, irradiated volume and mass

18F]FDG cardiac PET imaging in a canine model of radiation-induced cardiovascular disease associated with breast cancer radiotherapy.

Radiotherapy for the treatment of left-sided breast cancer increases the long-term risk of cardiovascular disease. The purpose of the present study was to noninvasively image the progression of radiation-induced cardiac inflammation in a large animal model using a hybrid PET and MRI system. Five canines were imaged using [18F]fluorodeoxyglucose PET to assess changes in myocardial inflammation. All animals were imaged at baseline, 1 wk, and 1, 3, 6, and 12 mo after focused cardiac external beam irradiation with image guidance. Radiation was delivered in a single fraction. The linear quadratic model was used to convert a typical multifractionated heart dose to a corrected single-fraction biologically equivalent dose. Immunohistochemistry was performed on excised left ventricular tissue samples from all five irradiated canines and one nonirradiated control canine to confirm the presence of inflammation. The mean doses delivered to the entire heart, left ventricle, left anterior descending artery, and left circumflex artery were 1.7 ± 0.2, 2.7 ± 0.2, 5.5 ± 0.9, and 1.1 ± 0.4 Gy, respectively. FDG standard uptake values remained persistently elevated compared with baseline (1.1 ± 0.03 vs. 2.6 ± 0.19, P < 0.05). The presence of myocardial inflammation was confirmed histologically and correlated with myocardial dose. This study suggests a global inflammatory response that is persistent up to 12 mo postirradiation. Inflammation PET imaging should be considered in future clinical studies to monitor the early changes in cardiac function that may play a role in the ultimate development of radiation-induced cardiac toxicity. NEW & NOTEWORTHY Using advanced cardiac PET imaging, we have shown the spatial and quantitative relationship between radiation dose deposition and temporal changes in inflammation. We have shown that the progression of radiation-induced cardiac inflammation is immediate and does not subside for up to 1 yr after radiation. Results are presented in a large animal model that closely resembles the size and vessel architecture of humans. The proposed imaging protocol can be easily replicated for clinical use.

Set-up Reproducibility for Deep Inspiration Breath Hold for Left Sided Breast Cancer Treatment Using Daily Mega Voltage Imaging-Integrated Network Study

Deep inspiration breath hold (DIBH) technique has been effective to reduce cardiac dose for left sided breast cancer treatment. However there are limited data on the setup reproducibility with DIBH technique. Herein we report the daily setup reproducibility and variation of DIBH using daily mega voltage (MV) imaging based on a large network of data. In total, 109 left breast cancer patients from 10 hospital sites across the UPMC Hillman Cancer Center network were treated using DIBH technique with daily MV imaging from May 2016 to July 2017. All patients had visual coaching via iPod device as well as voice coaching for DIBH for CT simulation and treatment. The same procedure and technique for DIBH CT simulation and treatment planning have been shared between physicists and physicians across the network. For each patient, BMI, age, surgery type (lumpectomy or mastectomy), regional and internal mammary nodes (IMN) involvement, MV imaging procedure used, number of total portal images and inter-fraction directional shifts were collected. For the statistical analyses, we separated all patients into two groups in each of the following three categories; 1) obese (BMI ≥ 30) vs. non- obese, 2) surgery type: mastectomy vs. lumpectomy, 3) internal mammary node (IMN) treatment vs. no IMN treatment. A total of 1833 treatments and 2818 MV portal images were analyzed. Minimum mean distance from heart to the tangential field edge was 2.5 mm (ranges 0-12 mm). The group mean inter-fraction directional shifts were as following: 1) 0.7 mm (superior; SD = 2.26), 0.8 mm (inferior; SD = 2.21), 2) 0.65 mm (left; SD =1.60), 0.64 mm (right; SD = 1.62), 3) 0.89 mm (anterior; SD = 1.96), 0.83 mm (posterior; SD=2.03). However between hospitals, there was found a difference in mean inter-fraction directional shift (p < 0.001). Any inter-fraction directional shift for ≥ 2mm, ≥ 3mm, ≥ 4mm, ≥ 5mm, ≥ 10mm was found to be 52.9 %, 37.6 %, 30.9 %, 21.9 %, 3.7 % of total fractions, respectively. In the stratified analysis, obese patients had larger directional shifts (p < 0.05) and highly associated with number of fractions for ≥ 5mm in any directional shift compared to non-obese patients (29 % vs. 17 %; p =0.04). To the best of our knowledge, this is the first and the largest study that reports the daily setup reproducibility and variation using MV images and patient’s visual feedback. DIBH setup for left breast cancer treatment at our large cancer center network was reproducible with any mean directional shifts less than 1.0 mm, although there was some inter-fraction variation between hospital sites. Consideration of daily imaging for obese patients should be taken to ensure the benefit of DIBH for that population. Also, if the distance of heart to the edge of the tangential treatment field is relatively close, it would be more beneficial to have daily imaging because 53 % of patients still had ≥ 2 mm shift.

Assessing Quality of Heart Contouring and Dosimetry in Treatment of Left Sided Breast Cancer Across Cancer Centers within an Integrated Health System

Cardiac sparing techniques in the treatment of left-sided breast cancer have led to a significant decrease in mean heart dose (MHD) over time. Inconsistency in contouring can impact accurate evaluation of cardiac dosimetry. Atlas Based Auto-Segmentation (ABS) can be used to reduce this inter-observer variability. We sought to assess quality of heart contouring and dosimetry across six radiation oncology departments within an integrated health system and assess the utility of ABS. We selected at random 60 patients (pts) treated with 3D conformal radiation therapy for left-sided breast cancer in 2017 at six centers within an integrated health system. A similar number of pts treated to left breast, chest wall (CW) or breast with regional lymph nodes (RNI), and CW or breast with RNI + internal mammary chain (IMC) were selected from each center. Doses were 40.05 Gy-50 Gy in 16-25 fractions. To account for different dose/fx regimens, treatment plans were scaled linearly to a dose of 50 Gy. Volumes and dosimetry for “gold standard” heart (GS-H), contoured based on RTOG 1005 and NSABP B51 protocol definitions, clinician contoured heart (C-H), and ABS generated heart (ABS-H) were compared using paired T-test. Volumes and dosimetry were compared across centers using one-way ANOVA. Dice coefficient was used to compare volume of overlap and Hausdorf distance was used to compare the distance between contours. There was no significant difference between the percentage of pts treated to left breast (p=0.97), CW or breast with RNI (p=0.50), and CW or breast with RNI + IMC (p=0.88) across centers. There was no significant difference in MHD (range 1.4 to 2.0; p=0.54), mean D1cc (range 20.5 to 35.2; p=0.22), and mean V5 (range 3.4% to 5.3%; p=0.92) across centers. However, a significant difference in cardiac volumes and dosimetry was observed for GS-H vs. ABS-H and GS-H vs. C-H (Table 1). We identified consistent cardiac dosimetry across six separate departments within an integrated health system. However, we identified heart contouring variability between GS-H and C-H techniques, which translated into statistically significant dosimetric differences, though quantitatively small. While current protocols recommend contouring heart to include the pericardium, C-H commonly excluded the pericardium, which may account for the dosimetric variability compared to GS-H. ABS-H, derived from clinician contours, should be adapted to reflect current protocol definitions.Abstract TU_9_3409: Table 1Comparison of Volume and Dosimetric Parameters Between Contouring MethodsGS-HABS-Hp-valueGS-HC-Hp-valueMean Heart Dose (Gy)1.81.6<0.0011.81.7<0.001Mean D1cc (Gy)26.122.3<0.00126.124.4<0.001Mean V5 (%)4.83.7<0.0014.84.3<0.001Mean V30 (%)0.70.50.0020.70.60.004Mean Dice Coefficient0.920.97Mean Hausdorf Distance0.200.09 Open table in a new tab

Changes in Cardiac MRI Derived Left Ventricular Segmental Strain in Left Sided Breast Cancer Patients Treated with Tangential Radioation Therapy Alone Correlated with Dose

Reduction in left ventricular global and segmental myocardial strain following tangential radiotherapy (RT) for left sided breast cancer treatment has been demonstrated using advanced echocardiographic techniques. This study aimed to determine if cardiac MRI (CMR), a more sensitive and precise imaging modality, could detect similar changes in segmental myocardial strain as per the American Heart Association(AHA) 16 segment model of the left ventricle in left sided breast cancer patients, and correlate this to RT dose. For 21 patients receiving left-sided breast RT, two serial CMR scans were obtained; immediately prior, and 4-6 weeks following RT. Single breath-hold Steady-State Free Precession (SSFP) Cine 2, 3, 4 chamber and short axis views were acquired, and using cvi42 tissue tracking software, two independent readings of 2D and 3D strain values were obtained, with the average being used for analysis. A linear mixed effects model was used to account for potential clustering of values between patients and segments. Multiple RT dosimetric values (including mean, max, V25) of each segment were calculated and their relationship with delta 2D/3D strain values explored. Median age was 59 years (range 38-76 years). Comprehensive nodal treatment using modified wide tangents using a deep inspiration breath hold technique (n=1) and the remainder received tangential breast radiation alone (n=20). No patient received chemotherapy. Two patients received 50Gy in 25 fractions, with 19/21 receiving 42.4Gy in 16 fractions. Median mean heart dose was 2.6Gy (1.5-3.9Gy). No difference was found between any pre and post RT strain parameters. These results are summarised in the table below.Abstract TU_12_3436: Table 1Strain ParameterPre-RT MeanPost-RT MeanDifference95% CIRadial 2D (Short Axis)54.5950.23-3.43[-8.8, 1.9]Circumference 2D (Short Axis)-23.11-22.150.73[-0.51, 2.0]Radial 2D (Long Axis)48.5647.460.07[-3.7, 3.8]Longitudinal 2D (Long Axis)-22.45-22.27-0.08[-0.80, 0.63]Radial 3D40.7737.85-2.17[-7.4, 3.1]Circumference 3D-20.05-19.200.72[-0.62, 2.1]Longitudinal 3D-19.49-18.920.47[-0.79, 1.7]Note the calculated differences are modelled quantities taking into account patients as a random effect and missing data. Therefore values in Difference column are not equal to pre RT mean minus post RT mean. When correlated with several radiation measures, there were no significant relationships between any radiation parameters and change in serial strain. Open table in a new tab Note the calculated differences are modelled quantities taking into account patients as a random effect and missing data. Therefore values in Difference column are not equal to pre RT mean minus post RT mean. When correlated with several radiation measures, there were no significant relationships between any radiation parameters and change in serial strain. No differences in left ventricular segmental strain were detected using CMR 4-6 weeks following left-sided breast radiotherapy, nor was there a clear relationship between RT dose and delta strain. Changes below the threshold of CMR detection given the lower temporal scanning resolution of CMR cannot be excluded. Longer term follow-up of this cohort will help determine if more delayed effects of radiation on LV function become manifest.

P274] A failure mode and effect analysis of deep inspiration breath-hold for left-sided breast cancer radiation therapy

Purpose The aim of this study was to assess the possible failure modes and analyze their consequences and effects in deep inspiration breath-hold radiation therapy. Methods Failure modes and effects analysis (FMEA) is step-by-step approach for identifying all possible failures in a process. Each step of the patient pathway for deep inspiration breath-hold radiation therapy was defined and four major process steps were created: patient initial clinical assessment, CT simulation, treatment planning and treatment delivery. For each process step 4–16 potential failure modes and effects were identified by the multidisciplinary team responsible for the FMEA. Each potential failure mode was scored for the likelihood of occurrence, potential severity and how easily it can be detected, depending on current departmental controls. Risk priority numbers (RPNs) were calculated as the product of occurrence, severity and detectability based on Task Group (TG)-100 scale [1] . Results RPNs were ranked from highest to lowest. Online imaging registration and patient positioning correction during treatment delivery, patient positioning and immobilization and patient preparation and coaching for deep inspiration breath-hold had the highest RPN 378, 210 and 168, respectively. Treatment planning check by a second medical physicist, patient positioning and set up instructions in the oncology information system had the lowest RPN score 10 and 32, respectively. Conclusions TG-100 recommends that FMEA can be used as a tool for risk and hazard analysis. An FMEA evaluation of deep inspiration breath-hold for left-sided breast cancer treatment can identify significant improvements in processes and increase in quality and safety of treatment delivery. Process steps with the highest RPNs must be addressed and new procedures must be introduced to minimize possible failures.