Deep Inspiration Breath Hold: Techniques and Advantages for Cardiac Sparing During Breast Cancer Irradiation

An upfront patient selection strategy based on personalized data-driven computed tomography generation for deep inspiration breath-hold in breast radiotherapy

BACKGROUND

Currently there is no widely used upfront selection method to determine whether patients are suitable for deep inspiration breath-hold (DIBH) in left-sided breast radiotherapy.

PURPOSE

To establish an upfront patient selection strategy to improve the decision-making efficiency of DIBH and avoid extra computed tomography (CT) exposure to patients.

METHODS

A total of 174 patients who underwent both free-breathing (FB) and DIBH scans were enrolled. A general principal component analysis model for DIBH-CT synthesis was trained and consists of principal component feature vectors extracted from paired FB-CT and DIBH-CT in training set. The coefficients of the vectors were optimized to minimize the difference between synthetic CT and breath-hold scout image of each patient in test set, leading to personalized DIBH-CT synthesis. An upfront patient selection strategy was established based on cardiac dose in synthetic DIBH-CT plan. The performance of DIBH-CT synthesis was analyzed in terms of geometric and dosimetric consistency between synthetic and scanned DIBH-CTs. The accuracy of the patient selection strategy was evaluated. Time assumption of the patient selection workflow was analyzed.

RESULTS

Synthetic DIBH-CTs had average Dice similarity coefficients of 0.84 for the heart and 0.91 for the lungs compared with scanned DIBH-CTs. Synthetic DIBH-CT plans revealed an average mean heart dose reduction of 1.46 Gy, which was not significantly different from 1.51 Gy in scanned DIBH-CT plans (p = 0.878). The patient selection strategy yielded the correct benefit results with accuracy of 86.7 %. The average time assumption for patient selection was 11.9 ± 3.6 min.

CONCLUSIONS

The proposed patient selection strategy can accurately identify patients benefiting from DIBH and provides a more efficient workflow for DIBH.

Patient coaching for deep inspiration breath hold decreases set-up duration and left anterior descending artery dose for left-sided breast cancer radiotherapy

PURPOSE

The purpose is to show the impact of patient coaching and home practice using the deep inspiration breath hold (DIBH) technique on radiation treatment set-up times and cardiac at-risk doses.

METHODS

The study involved patients who received tangential field radiotherapy using the DIBH technique for treating left breast cancer. Patients were divided into two groups: the first group consisted of those who received coaching from an oncology nurse and were given an instruction sheet at least 1 week before the computed tomography (CT) simulation. The second group consisted of those who were only taught how to hold their breath by the radiation technician on the simulation day and without further education. During treatment, the patients were monitored using the Varian RPM™ respiratory gating system, and 2D kV orthogonal imaging was performed daily. The setup duration of each patient was noted and compared between treatment groups. For each patient, the dose-volume histograms (DVHs) of the heart, LAD (left anterior descending artery), were calculated and compared for both coached DIBH (cDIBH) and non-coached DIBH (ncDIBH).

RESULTS

Thirty-six coached and 28 non-coached patients were identified. Compared with ncDIBH, coached patients were older (55.5 versus 46.5, p = 0.003) and had a significantly higher BMI (body mass index) (29.95 versus 26.32 kg/m2, p = 0.006). Nevertheless, in more than half of the treatment fractions, the set-up duration was detected to be statistically longer in the ncDIBH group than in the cDIBH group. Additionally, the LAD max dose was significantly lower in the cDIBH group (36.5 versus 29.5, p = 0.02).

CONCLUSION

Coaching at least 1 week before the simulation with an instruction sheet decreased the set-up duration, and the cardiac LAD max dose should be further decreased by this method.

Comparative analysis of radiotherapy modalities and techniques for left breast cancer: dose coverage, setup accuracy, with patient-specific selection criteria for applying deep inspiration breath hold

To compare dosimetric outcomes between Free Breath (FB) and Deep Inspiration Breath Hold (DIBH) across different radiotherapy modalities, establish patient selection criteria for DIBH, and optimizing the setup margin (SM) in left breast cancer treatment. 26 patients with left breast cancer were studied at CRO, Aviano in Italy. FB and DIBH simulations were done using CT with a real-time position management system. 3DCRT and IMRT plans were prepared for both simulations of each patient. The setup margin was measured by Van Herk's formula and compared with residual uncertainties. The dose coverage of PTV and spare OARs were better with DIBH. The distance of more than 1.6 cm between (Left Anterior Descending artery) LAD and PTV was no significantly different for FB and DIBH. The setup margin by Van Herk's formula was calculated as 0.9 cm for DIBH_IMRT. The average duration of DIBH per respiration was 19 ± 4 s. So, holding one breath at least 19 s would be the criteria for choosing a patient to apply DIBH. DIBH enhances PTV dose coverage and OAR sparing in both 3DCRT and IMRT. When the distance between the LAD and PTV exceeds 1.6 cm, the application of DIBH depends on the availability of a LINAC with RPM and the patient's breathholding ability.

Cardiac Complications of Radiation Therapy

Radiation therapy is a critical component in managing many malignancies by improving local control and survival. The benefits of radiation may come at the expense of unintended radiation injury to the surrounding normal tissues, with the heart being one of the most affected organs in thoracic radiation treatments. As cancer survivors live longer, radiation-induced cardiotoxicity (RICT) is now increasingly recognized. In this review, we highlight the spectrum and pathophysiology of RICT. We summarize contemporary recommendations for risk stratification, screening, prevention, and management of RICT. We briefly highlight novel applications for radiation to treat some cardiac conditions such as resistant arrhythmias.

Strategies to Reduce Left Anterior Descending Artery and Left Ventricle Organ Doses in Radiotherapy Planning for Left-Sided Breast Cancer

Background

One of the most significant long-term toxicities of breast cancer radiotherapy is major adverse cardiac events (MACE). In current radiotherapy practice, the mean heart dose is the most commonly used parameter. The aim of our study was to reduce the doses of organs at risk (OAR) in the left anterior descending artery (LAD) and left ventricle (LV) by including the LAD and LV in planning radiotherapy while maintaining adequate dose coverage for patients with left-sided breast cancer.

Methods

We retrospectively analyzed left-sided breast cancer cases treated at the Kocaeli University Faculty of Medicine. Only patients with local and locally advanced breast cancer were included in the analysis. A total of 77 patients who were treated between 2020 and 2024 were included. The doses to the LAD and LV were added to the optimization algorithms. Two volumetric modulated arc therapy (VMAT) plans were created for each patient. A total of 154 plans were made, including standard and LAD and LV sparing plans.

Results

There was no statistically significant difference in all VMAT plans regarding planning target volume (PTV) D2, D50, and D98 (dose receiving volume of PTV 2%, 50%, and 98%) (p > 0.05). However, a significant decrease was observed in heart V5 (the percentage of the heart receiving at least 5 gray (Gy)) and mean heart dose. A decrease in the mean heart dose was observed in the standard plan compared with the LAD and LV sparing plan (p < 0.001). Similarly, the heart V5 value decreased significantly (p < 0.001). Additionally, significant reductions were measured in all LAD and LV parameters after re-optimization.

Conclusions

We achieved significant reductions in all heart, LAD, and LV parameters without making any changes to the planned treatment volume coverage by adding LAD and LV OARs to the optimization algorithms. The potential risk of MACE can be significantly reduced by implementing this strategy.

Visual Dose Monitoring for Whole Breast Radiation Therapy Treatments via Combined Cherenkov Imaging and Scintillation Dosimetry

PURPOSE

This study investigates scintillation dosimetry coupled with Cherenkov imaging for in vivo dose monitoring during whole breast radiation therapy (WBRT). Given recent observations of excess dose to the contralateral breast (CB), in vivo dosimetry (IVD) could help ensure accurate dose delivery and decrease risks of secondary cancer. This work presents a rapid, streamlined alternative to traditional IVD, providing direct visualization of measurement location relative to the treatment field on the patient.

METHODS AND MATERIALS

Ten WBRT patients consented under an institutional review board-approved protocol were monitored with scintillation dosimetry and always-on Cherenkov imaging, on both their treated and CB for 1 to 3 fractions. Scintillator dosimeters, small plastic discs 1 mm thick and 15 mm in diameter, were calibrated against optically stimulated luminescent dosimeters (OSLDs) to generate an integral output-to-dose conversion, where integral output is measured in postprocessing through a custom fitting algorithm. The discs have been extensively characterized in a previous study for various treatment conditions including beam energy and treatment geometry.

RESULTS

A total of 44 dosimetry measurements were evaluated, including 22 treated breast and 22 CB measurements. After integral output-to-dose calibration, in vivo scintillator dosimeters exhibited high linearity (R2 = 0.99) with paired OSLD readings across all patients. The difference between scintillation and OSLD dose measurements averaged 2.8% of the prescribed dose, or an absolute dose difference of approximately 7 cGy.

CONCLUSIONS

Integration of scintillation dosimetry with Cherenkov imaging offers an accurate, rapid alternative for in vivo dose verification in WBRT, circumventing the limitations of conventional point dosimeters. The additional benefit of visualizing measurement locations relative to the treatment field provides users an enhanced understanding of results and allows for detection of high dose gradients. Future work will explore the applicability of this technique across a broader range of radiation therapy treatments, aiming to streamline IVD practices.

Dose comparison between hybrid volumetric modulated arc therapy, volumetric modulated arc therapy, and three-dimensional conformal radiotherapy for breast/chest wall irradiation, including regional lymph node irradiation using deep inspiration breath-hold technique

PURPOSE

Breast radiation treatment has been linked to complications such as pneumonitis and cardiac toxicity, necessitating dose optimization. This study aims to determine the optimal integration plan of volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) in a deep inspiration breath-hold regimen.

MATERIALS AND METHODS

CT imaging data from twenty patients with breast or chest wall cancer, either right or left-sided, and with supraclavicular and internal mammary chain lymph nodes were retrieved. The CT data planned with a hybrid VMAT of three different weighting proportions: 30 % using 3DCRT and 70 % using VMAT, 50 % using 3DCRT and 50 % using VMAT, and 70% using 3DCRT and 30 % using VMAT and compared with full 3DCRT and full VMAT plan (classic and five arc design).

RESULTS

The homogeneity and conformity indices were better in the hybrid VMAT plans than in plans using VMAT or 3DCRT alone (P<0.005). Results of all hybrid VMAT plans showed a considerable drop of volumes receiving more than 4Gy, 8Gy or 16Gy in the ipsilateral lung compared to the full VMAT plan (P<0.001). There was a noticeable decrease in the mean dose to the heart and the dose in 5% of the contralateral breast in the plan using 70 % 3DCRT and 30 % VMAT compared to full VMAT (P<0.001). The plan using 70 % 3DCRT and 30% VMAT achieved a balance between the target and surrounding areas, compared to using only 3DCRT or VMAT.

CONCLUSION

A hybrid plan using 70 % 3DCRT contribution achieved a balanced outcome for breast or chest wall irradiation, considering both planning target volume and organs at risk. Utilizing our VMAT arc design, incorporating one shortened arc can significantly reduce doses to organs at risk further. It is important to consider the patient's anatomy when making this decision.

Comparing Interfractional Stability of Heart Dose Among Three Breath-Hold Radiotherapy Techniques in Breast Cancer

AIMS

Breath holding can reduce the cardiac dose in radiotherapy for left-sided breast cancer. We evaluated whether any of the existing commonly used breath-hold techniques was superior in maintaining a more reproducible mean heart dose (MHD) during treatment.

MATERIALS AND METHODS

This was a single-institution, interventional, nonrandomised, three-armed prospective trial, comparing the reproducibility of MHD in breath-hold radiotherapy using voluntary deep inspiration breath hold (vDIBH), active breathing control (ABC), and surface-guided radiotherapy (SGRT). The MHDs were determined based on the anatomy in planning computed tomography (CT) and each weekly cone beam computed tomography (CBCT) during radiotherapy. The reproducibility of MHD was measured by calculating the interfractional variation of MHD (represented by the standard deviation) across the CBCT and the difference between the cumulative MHD at CBCT and at planning CT. These two measures of reproducibility were then compared among vDIBH, ABC, and SGRT.

RESULTS

Of the 55 patients recruited, 19 had ABC, 20 had SGRT, and 16 had vDIBH. SGRT was associated with a slightly greater interfractional variation of the MHD than vDIBH (least squares mean (LSM): 28.8 cGy (SGRT) vs 10.5 cGy (vDIBH), P = 0.0052) and ABC (LSM: 28.8 cGy (SGRT) vs 15.1 cGy (ABC), P = 0.026). In the SGRT group, the cumulative MHD at CBCT was lower than that at planning CT (mean difference: -22.1 cGy, P = 0.013). No such difference existed in vDIBH and ABC. In terms of the reproducibility of cumulative MHD at CBCT as compared to that in planning CT, there was no significant difference between vDIBH (mean: -12.1 cGy), ABC (mean: -4.8 cGy), and SGRT (mean: -22.1 cGy) (P value for pairwise comparison: all >0.1).

CONCLUSIONS

SGRT was associated with a slightly greater interfractional variation of MHD than vDIBH and ABC, but the difference may not be clinically significant. All three breath-hold techniques were broadly comparable in their reproducibility of MHD at CBCT relative to the planning CT.

Investigating the effects of table movement and sag on optical surrogate-driven respiratory-guided computed tomography

PURPOSE

Respiratory-guided computed tomography (CT) typically employs breathing motion surrogates to feed image reconstruction or visual breathing coaching. Our study aimed to assess the impact of table movements and table sag on the breathing curves recorded in four-dimensional (4D) CT and deep-inspiration breath-hold (DIBH) CT.

METHODS

For breathing curve measurements, static and dynamic phantom scenarios were used. Breathing curves were recorded using three different surrogate systems and the impact of table sag due to weights of up to 130 kg was analyzed and compared to a non-weighted setting, respectively. The calibration procedure of the system used as an input for the visual coaching device used for clinical DIBH CT scans was adapted. We evaluated corresponding breathing curves acquired during DIBH and 4DCT scans of altogether 70 patients using various stability metrics.

RESULTS

The various surrogate systems showed consistent table sag measurements below 4 mm, even under loads up to 130 kg, compared to a reference scan conducted without additional weight. Higher weight loads were related to steeper table sag fall-offs towards the deepest table position. For DIBH CT scans, the visual guidance was heavily affected by artifacts. This resulted in breathing threshold limits, which could not be achieved by 48% (n = 21) of the, respectively, examined patients. Using the new calibration workflow, the baseline drift was compensated better and 90% (n = 20) of the addressed patients stayed within the thresholds. The evaluated table sag in clinical 4DCT scans (n = 29) stayed below 3 mm compared to the non-weighted situation.

CONCLUSION

Table movement and sag can impact breathing curves recorded by different surrogate systems. Correcting table movement and sag artifacts is crucial for reliable breathing curve acquisition in respiratory-guided CT.

Quality of life in early breast cancer patients after adjuvant accelerated partial-breast irradiation (APBI) in randomized trial

Accelerated partial breast irradiation (APBI) represents a valid option for adjuvant therapy of selected early breast cancer (BC). This single-institution prospective randomized study compares the health-related quality of life (HRQoL) between women treated with the highly conformal-external beam APBI technique and those with the more commonly used moderately hypofractionated whole breast irradiation (hypo-WBI). Eligible patients were women over 50 years with early BC (G1/2 DCIS ≤ 25 mm or G1/2 invasive non-lobular luminal-like HER2 negative carcinoma ≤ 20 mm) after breast-conserving surgery with negative margins. APBI arm consisted of 30 Gy in 5 consecutive daily fractions and WBI arm of 40 Gy in 15 fractions plus 10 Gy in 5 fractions boost to the tumor bed. Patients were requested to complete the official Czech translation of the EORTC QoL questionnaires, including QLQ-C30 and QLQ-BR45, before radiation (baseline), at the end of radiation (M0) and 1 (M1), 3 (M3), 6 (M6), 12 (M12), and 24 (M24) months after radiation. Linear regression models were used to analyze differences in HRQoL between the arms. The 85 enrolled patients exhibited no differences in HRQoL scores between the two arms at baseline. Patients in the APBI arm reported more favorable global health status at M6 (p = 0.055). Other functional scales showed a decrease in the WBI arm at M0 (p = 0.027 for physical functioning). During radiation, symptoms scores increased. Significant between-group differences were observed for the pain (p = 0.002), systemic therapy side effects (p = 0.004), and breast symptoms (p < 0.001) scales at M0, with higher scores in the WBI arm. During follow-up, scores on symptoms scales returned to at least the baseline values. Early BC patients treated with APBI showed non-inferior short-term and late HRQoL outcomes compared to hypo-WBI. In addition to previous findings regarding toxicity, promising pain and breast symptoms results, suggest that APBI should be strongly considered as a treatment option for selected low-risk patients.Trial registration NCT06007118, August 23, 2023 (retrospectively registered).

A Study on Synchronous Bilateral Breast Cancer Radiotherapy Based on an Accelerator Integrated with Optical Surface Monitoring System

OBJECTIVE

To investigate the optimal radiotherapy regimen for synchronous bilateral breast cancer (SBBC) by utilizing dosimetric and radiobiological indicators, and to assess the impact of applying an optical surface monitoring system(OSMS) on the precision of SBBC radiotherapy treatment.

METHODS

Nine patients with SBBC who underwent breast-conserving radiotherapy were retrospectively selected. Four treatment plans were designed for each patient using the Versa HD (Elekta, Stockholm) accelerator: single-isocenter intensity-modulated radiotherapy/volumetric modulated arc therapy(IMRT-ISO1/VMAT-ISO1) and dual-isocenter IMRT/VMAT(IMRT-ISO2/VMAT-ISO2), with a prescription dose of 42.4 Gy in 16 fractions. Dosimetric parameters and radiobiological impact were measured for the target and organs at risk(OARs). The monitoring log files of three SBBC patients were analyzed to quantitatively assess real-time delta shifts encompassing six degrees of freedom (DOFs) during intrafraction and interfraction treatment processes.

RESULTS

Compared to both the IMRT techniques, the VMAT techniques offered superior target conformity, uniformity, and dose fall-off capability. Among the four treatment plans, VMAT-ISO1 exhibited optimal performance by significantly reducing radiation exposure volume to OARs while maintaining exceptional precision in dose delivery and execution efficiency. The tumor control probability (TCP) was exceeded by 98.5% for all four modalities. According to the OSMS logs, the maximum absolute error in translational motion during the treatment of three SBBC patients was predominantly manifested along the vertical(VRT) axis, with an mean value of 2.2 mm. Additionally, it was observed that the coronal plane (YAW) exhibited the largest error in terms of rotational angle, with an mean deviation of 1.1°.

CONCLUSIONS

The VMAT-ISO1 technique demonstrates apparent dosimetric and radiobiological advantages in SBBC radiotherapy, ensuring precise dose delivery and shortening treatment durations. The accuracy of SBBC radiotherapy is ensured by OSMS through pre-treatment positioning correction and real-time monitoring throughout the treatment process.

S, Nisha R, Nair S, Nagesh J, Chandraguthi S. A Prospective Study on the Use of Deep Inspiration Breath-Hold Technique in External Beam Radiotherapy for Breast Cancer

Background

Breast cancer is the most common cancer and the leading cause of death in women. The deep inspiration breath-hold (DIBH) technique helps reduce the dose received by the heart and lungs in breast cancers during adjuvant radiotherapy (RT). We present the dosimetry of heart and lungs with DIBH technique, reproducibility, and ease of execution.

Materials and Methods

This is a prospective study among breast cancer patients planned for adjuvant RT following either breast conservation or mastectomy. Patients received adjuvant RT to a dose of 42.5 Gy/16 Fr to the chest wall/whole breast followed by a boost of 10 Gy/5 Fr for breast conservation surgery patients with either three-dimensional conformal RT or volumetric modulated arc therapy technique. The dosimetric parameters such as lung mean dose, heart mean dose, and V25 Gy were compared between DIBH and free-breathing (FB) scans. Data were analyzed using SPSS software, and p -value <0.05 was considered statistically significant.

Results

The study was conducted from September 2018 to August 2020, and 32 patients were included. The compliance to the DIBH technique was good. The dose received by ipsilateral lung V20 (17 vs. 25%) and mean dose (9 vs. 12 Gy) were significantly lower in DIBH compared with FB ( p  < 0.001). The V5 (31 vs. 15%), V25 (9 vs. 2%), and mean dose (7 vs. 3.3 Gy) to the heart were much higher in FB compared with DIBH ( p  < 0.001).

Conclusion

DIBH-based RT treatment delivery for breast cancer patients requiring adjuvant RT showed good compliance and offers a significant reduction in radiation dose to the heart and lung.

Cardiac substructure delineation in radiation therapy - A state-of-the-art review

Delineation of cardiac substructures is crucial for a better understanding of radiation-related cardiotoxicities and to facilitate accurate and precise cardiac dose calculation for developing and applying risk models. This review examines recent advancements in cardiac substructure delineation in the radiation therapy (RT) context, aiming to provide a comprehensive overview of the current level of knowledge, challenges and future directions in this evolving field. Imaging used for RT planning presents challenges in reliably visualising cardiac anatomy. Although cardiac atlases and contouring guidelines aid in standardisation and reduction of variability, significant uncertainties remain in defining cardiac anatomy. Coupled with the inherent complexity of the heart, this necessitates auto-contouring for consistent large-scale data analysis and improved efficiency in prospective applications. Auto-contouring models, developed primarily for breast and lung cancer RT, have demonstrated performance comparable to manual contouring, marking a significant milestone in the evolution of cardiac delineation practices. Nevertheless, several key concerns require further investigation. There is an unmet need for expanding cardiac auto-contouring models to encompass a broader range of cancer sites. A shift in focus is needed from ensuring accuracy to enhancing the robustness and accessibility of auto-contouring models. Addressing these challenges is paramount for the integration of cardiac substructure delineation and associated risk models into routine clinical practice, thereby improving the safety of RT for future cancer patients.

Rapid Selection of Patients Suitable for Deep Inspiration Breath-Hold Using an Automatic Delineating System and RapidPlan Model in Patients With Left Breast Cancer Undergoing Adjuvant Radiation Therapy With IMRT

PURPOSE

This study aimed to determine whether radiation therapy plans created using an automatic delineating system and a RapidPlan (RP) module could rapidly and accurately predict heart doses and benefit from deep inspiratory breath-hold (DIBH) in patients with left breast cancer.

METHODS AND MATERIALS

One hundred thirty-six clinically approved free breathing (FB) plans for patients with left breast cancer were included, defined as manual delineation-manual plan (MD-MP). A total of 104 of 136 plans were selected for RP model training. A total of 32 of 136 patients were automatically delineated by software, after which the RP generated plans, defined as automatic delineation-RapidPlan (AD-RP). In addition, 40 patients who used DIBH were included to analyze differences in heart benefits from DIBH.

RESULTS

Two RP models were established for post-breast-conserving surgery (BCS) and post-modified radical mastectomy. There were no significant differences in most of the dosimetric parameters between the MD-MP and AD-RP. The heart doses of the 2 plans were strongly correlated in patients after BCS (0.80 ≤ r ≤ 0.88, P < .05) and moderately correlated in patients after postmodified radical mastectomy (0.46 ≤ r ≤ 0.58, P <.05). The RP model predicted the mean heart dose (MHD) within ± 59.67 cGy and ± 63.32 cGy for patients who underwent the 2 surgeries described above. The heart benefits from DIBH were significantly greater in patients with FB-MHD ≥ 4 Gy than in those with FB-MHD < 4 Gy.

CONCLUSIONS

The combined automatic delineation RP model allows for the rapid and accurate prediction of heart dose under FB in patients with left breast cancer. FB-MHD ≥ 4 Gy can be used as a dose threshold to select patients suitable for DIBH.

Impact of deep inspiration breath hold, surface-guided radiotherapy, and daily CBCT on the organs at risk in breast cancer radiotherapy

The goal of the study was to assess the impact of deep inspiration breath hold technique (DIBH), surface-guided radiotherapy (SGRT), and daily kilovoltage cone-beam computed tomography (kV-CBCT) on the dose to organs at risk (OAR) in left-sided breast cancer radiotherapy. Twenty-six consecutive left-sided breast cancer patients treated using Volumetric Intensity Modulated Arc Therapy (VMAT), DIBH, SGRT, and a hypofractionated regimen were retrospectively evaluated in this study. Dose parameters were extracted from dose-volume histograms (DVH). The Wilcoxon Matched Pairs test was used to test dose parameters obtained in free breathing (FB) and DIBH for statistical significance. Multivariable analysis of variance (ANOVA) and receiver operating characteristics (ROC) analysis were used to identify parameters and cut-off points associated with the reduction of the mean heart dose (MHD) by DIBH. Based on published models, the risk of cardiac and lung toxicity (pneumonitis) using SGRT or daily kV-CBCT was estimated and compared. DIBH substantially reduced the MHD (median, 43.6%; range, 4.2% to 75.1%; P < 0.00001). The risk of cardiac toxicity using SGRT increased by 1%, compared to 3.6% to 20.5% using daily kV-CBCT. No significant difference in the risk of radiation-induced pneumonitis using SGRT versus daily kV-CBCT was detected. The ANOVA revealed the relative increase of the left lung volume by DIBH as the only significant impact factor for the MHD. The ROC analysis of this parameter showed an area under the curve (AUC) of 0.89 (95%CI, 0.71 to 0.98; P < 0.0001). DIBH can substantially reduce the MHD in left-sided breast cancer patients treated with modern radiotherapy techniques and hypofractionation. Patient setup using SGRT compared to daily kV-CBCT may be the preferred option for many patients. In our patient cohort, the relative reduction of the left lung volume by DIBH can be used as a predictor to select patients who benefit from DIBH.

Dosimetric benefit and clinical feasibility of deep inspiration breath-hold and volumetric modulated arc therapy-based postmastectomy radiotherapy for left-sided breast cancer

To evaluate the dosimetric benefits and clinical feasibility of deep inspiratory breath-hold (DIBH) combined with volumetric modulated arc therapy (VMAT) in left-sided postmastectomy radiotherapy (PMRT). Eligible patients with left-sided breast cancer undergoing DIBH-based PMRT were prospectively included. Chest wall, supra/infraclavicular fossa, and/or internal mammary node irradiation (IMNI) were planned with a prescription dose of 43.5 Gy in 15 fractions. VMAT plans were designed on free breathing (FB)-and DIBH-CT to compare dosimetric parameters in heart, left anterior descending artery (LAD) and lung. Cone-beam computed tomography (CBCT) was performed before and after treatment to evaluate inter- and intra-fractional setup errors. Heart position and dose variations during treatment were estimated by fusing CBCT with DIBH-CT scans.Twenty patients were included with 10 receiving IMNI. In total, 193 pre-treatment and 39 pairs pre- and post-treatment CBCT scans were analyzed. The Dmean, Dmax, and V5-40 of the heart, LAD, and left lung were significantly lower in DIBH than FB (p < 0.05 for all), except for V5 of LAD (p = 0.167). The cardiopulmonary dosimetric benefits were maintained regardless of IMNI. The inter- and intra-fractional setup errors were < 0.3 cm; and the overall estimated PTV margins were < 1.0 cm. During treatment, the mean dice similarity coefficient of heart position and the mean ratio of heart Dmean between CBCT and DIBH-CT plans was 0.95 (0.88-1.00) and 100% (70.6-119.5%), respectively. DIBH-VMAT could effectively reduce the cardiopulmonary doses with acceptable reproducibility and stability in left-sided PMRT regardless of IMNI.

Analysis of Planning Risk Volume for Heart during Radiotherapy Delivery with Breath-Hold Technique for Carcinoma of Left Breast

Purpose

The purpose of the study was to analyze and estimate planning risk volume (PRV) margin for heart in deep inspiration breath hold (DIBH)-based left breast radiotherapy.

Materials and Methods

Fifty left-sided cancer breast cases treated with volumetric modulated arc radiotherapy were included in this retrospective study. Treatment plans were created using the Eclipse treatment planning system from Varian Medical System. The treatment was delivered on TrueBeam linear accelerator (Varian). Onboard cone-beam computed tomography (CBCT) images were generated and image registration between the planning computed tomography images and the CBCT images was performed before treatment delivery. The registration provided the shifts (errors) values in 6° of freedom, namely three translational and three rotational. From the shift values, the systematic and random errors were estimated which were used to estimate PRV margin for the heart after incorporating the rotational errors with the translational errors.

Results

The systematic error values after incorporating rotational errors with translational errors were 0.13 cm (lateral) and 0.11 cm (cranio caudal [CC] and anterioposterior each), and the random error values were 0.16 cm (lateral) and 0.13 cm (CC and anterioposterior each). Based on these values, the PRV margins for the heart in all three directions were 0.24 cm (lateral), 0.20 cm (CC), and 0.19 cm (anterioposterior).

Conclusion

As per our institutional practice, the 2 mm value for PRV margin for the heart in all the three directions would suffice for appropriate sparing of the heart during DIBH-based radiation therapy.

Laterality of Radiation Therapy in Breast Cancer is Not Associated With Increased Risk of Coronary Artery Disease in the Contemporary Era

Purpose

External beam radiation therapy (EBRT) is a critical component of breast cancer (BC) therapy. Given the improvement in technology in the contemporary era, we hypothesized that there is no difference in the development of or worsening of existing coronary artery disease (CAD) in patients with BC receiving left versus right-sided radiation.

Methods and Materials

For the meta-analysis portion of our study, we searched PubMed, Web of Science, and Scopus and included studies from January 1999 to September 2022. CAD was identified using a homogenous metric across multiple studies included. We computed the risk ratio (RR) for included studies using a random effects model. For the institutional cohort portion of our study, we selected high cardiovascular-risk patients who received diagnoses of BC between 2010 and 2022 if they met our inclusion criteria. We performed a Cox proportional hazards model with stepwise adjustment.

Results

A pooled random effects model with 9 studies showed that patients with left-sided BC receiving EBRT had a 10% increased risk of CAD when compared with patients with right-sided BC receiving EBRT (RR, 1.10; 95% CI, 1.02-1.18; P = .01). However, subgroup analysis of 6 studies that included patients diagnosed after 1980 did not show a significant difference in CAD based on BC laterality (RR, 1.07; 95% CI, 0.95-1.20; P = .27). For the institutional cohort portion of the study, we found that patients with left-sided BC who received EBRT did not have a significantly higher risk of CAD when compared with their right-sided counterparts (hazard ratios [HR], 0.73; 95% CI, 0.34-1.54; P = .402).

Conclusions

Our study suggests a historical trend of increased CAD in BC patients receiving left-sided EBRT. Data from patients diagnosed after 2010 in our institutional cohort did not show a significant difference, emphasizing that modern EBRT regimens are safe, and laterality of BC does not affect CAD outcomes in the short term after a BC diagnosis.

Clinical practicality and patient performance for surface-guided automated VMAT gating for DIBH breast cancer radiotherapy

BACKGROUND AND PURPOSE

To evaluate the performance of automated surface-guided gating for left-sided breast cancer with DIBH and VMAT.

MATERIALS AND METHODS

Patients treated in the first year after introduction of DIBH with VMAT were retrospectively considered for analysis. With automated surface-guided gating the beam automatically switches on/off, if the surface region of interest moved in/out the gating tolerance (±3 mm, ±3°). Patients were coached to hold their breath as long as comfortably possible. Depending on the patient's preference, patients received audio instructions during treatment delivery. Real-time positional variations of the breast/chest wall surface with respect to the reference surface were collected, for all three orthogonal directions. The durations and number of DIBHs needed to complete dose delivery, and DIBH position variations were determined. To evaluate an optimal gating window threshold, smaller tolerances of ±2.5 mm, ±2.0 mm, and ±1.5 mm were simulated.

RESULTS

525 fractions from 33 patients showed that median DIBH duration was 51 s (range: 30-121 s), and median 4 DIBHs per fraction were needed to complete VMAT dose delivery. Median intra-DIBH stability and intrafractional DIBH reproducibility approximated 1.0 mm in each direction. No large differences were found between patients who preferred to perform the DIBH procedure with (n = 21) and without audio-coaching (n = 12). Simulations demonstrated that gating window tolerances could be reduced from ±3.0 mm to ±2.0 mm, without affecting beam-on status.

CONCLUSION

Independent of the use of audio-coaching, this study demonstrates that automated surface-guided gating with DIBH and VMAT proved highly efficient. Patients' DIBH performance far exceeded our expectations compared to earlier experiences and literature. Furthermore, gating window tolerances could be reduced.

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

INTRODUCTION

The 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 METHODS

The 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.

RESULTS

The 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.

CONCLUSION

Our 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.

Setup margins based on the inter- and intrafractional setup error of left-sided breast cancer radiotherapy using deep inspiration breath-hold technique (DIBH) and surface guided radiotherapy (SGRT)

PURPOSE

The use of volumetric modulated arc therapy (VMAT), simultaneous integrated boost (SIB), and hypofractionated regimen requires adequate patient setup accuracy to achieve an optimal outcome. The purpose of this study was to assess the setup accuracy of patients receiving left-sided breast cancer radiotherapy using deep inspiration breath-hold technique (DIBH) and surface guided radiotherapy (SGRT) and to calculate the corresponding setup margins.

METHODS

The patient setup accuracy between and within radiotherapy fractions was measured by comparing the 6DOF shifts made by the SGRT system AlignRT with the shifts made by kV-CBCT. Three hundred and three radiotherapy fractions of 23 left-sided breast cancer patients using DIBH and SGRT were used for the analysis. All patients received pre-treatment DIBH training and visual feedback during DIBH. An analysis of variance (ANOVA) was used to test patient setup differences for statistical significance. The corresponding setup margins were calculated using the van Herk's formula.

RESULTS

The intrafractional patient setup accuracy was significantly better than the interfractional setup accuracy (p < 0.001). The setup margin for the combined inter- and intrafractional setup error was 4, 6, and 4 mm in the lateral, longitudinal, and vertical directions if based on SGRT alone. The intrafractional error contributed ≤1 mm to the calculated setup margins.

CONCLUSION

With SGRT, excellent intrafractional and acceptable interfractional patient setup accuracy can be achieved for the radiotherapy of left-sided breast cancer using DIBH and modern radiation techniques. This allows for reducing the frequency of kV-CBCTs, thereby saving treatment time and radiation exposure.

Personalized Radiation Therapy for Breast Cancer

Breast cancer is diagnosed in nearly 3 million people worldwide. Radiation therapy is an integral component of disease management for patients with breast cancer, and is used after breast-conserving surgery or a mastectomy to reduce the risk of a local recurrence. The following review describes the methods used to personalize radiation therapy by optimizing patient selection, using advanced treatment techniques to lessen the radiation dose to normal organs, and using hypofractionation in order to shorten the duration of radiation treatment.

Factors Associated With Cardiac Radiation Dose Reduction After Hypofractionated Radiation Therapy for Localized, Left-Sided Breast Cancer in a Large Statewide Quality Consortium

PURPOSE

Limiting cardiac radiation dose is important for minimizing long-term cardiac toxicity in patients with left-sided early-stage breast cancer.

METHODS AND MATERIALS

Prospectively collected dosimetric data were analyzed for patients undergoing moderately hypofractionated radiation therapy to the left breast within the Michigan Radiation Oncology Quality Consortium from 2016 to 2022. The mean heart dose (MHD) goal was progressively tightened from ≤2 Gy in 2016 to MHD ≤ 1.2 Gy in 2018. In 2021, a planning target volume (PTV) coverage goal was added, and the goal MHD was reduced to ≤1 Gy. Multivariate logistic regression models were developed to assess for covariates associated with meeting the MHD goals in 2016 to 2020 and the combined MHD/PTV coverage goal in 2021 to 2022.

RESULTS

In total, 4165 patients were analyzed with a median age of 64 years. Overall average cardiac metric compliance was 91.7%. Utilization of motion management increased from 41.8% in 2016 to 2020 to 46.5% in 2021 to 2022. Similarly, use of prone positioning increased from 12.2% to 22.2% in these periods. On multivariate analysis in the 2016 to 2020 cohort, treatment with motion management (odds ratio [OR], 5.20; 95% CI, 3.59-7.54; P < .0001) or prone positioning (OR, 3.21; 95% CI, 1.85-5.57; P < .0001) was associated with meeting the MHD goal, while receipt of boost (OR, 0.25; 95% CI, 0.17-0.39; P < .0001) and omission of hormone therapy (OR, 0.65; 95% CI, 0.49-0.88; P = .0047) were associated with not meeting the MHD goal. From 2021 to 2022, treatment with motion management (OR, 1.89; 95% CI, 1.12-3.21; P = .018) or prone positioning (OR, 3.71; 95% CI, 1.73-7.95; P = .0008) was associated with meeting the combined MHD/PTV goal, while larger breast volume (≥1440 cc; OR, 0.34; 95% CI, 0.13-0.91; P = .031) was associated with not meeting the combined goal.

CONCLUSIONS

In our statewide consortium, high rates of compliance with aggressive targets for limiting cardiac dose were achievable without sacrificing target coverage.

Toxicity of external beam accelerated partial-breast irradiation (APBI) in adjuvant therapy of early-stage breast cancer: prospective randomized study

BACKGROUND

Accelerated partial breast irradiation (APBI) is an alternative breast-conserving therapy approach where radiation is delivered in less time compared to whole breast irradiation (WBI), resulting in improved patient convenience, less toxicity, and cost savings. This prospective randomized study compares the external beam APBI with commonly used moderate hypofractionated WBI in terms of feasibility, safety, tolerance, and cosmetic effects.

METHODS

Early breast cancer patients after partial mastectomy were equally randomized into two arms- external APBI and moderate hypofractionated WBI. External beam technique using available technical innovations commonly used in targeted hypofractionated radiotherapy to minimize irradiated volumes was used (cone beam computed tomography navigation to clips in the tumor bed, deep inspiration breath hold technique, volumetric modulated arc therapy dose application, using flattening filter free beams and the six degrees of freedom robotic treatment couch). Cosmetics results and toxicity were evaluated using questionnaires, CTCAE criteria, and photo documentation.

RESULTS

The analysis of 84 patients with a median age of 64 years showed significantly fewer acute adverse events in the APBI arm regarding skin reactions, local and general symptoms during a median follow-up of 37 months (range 21-45 months). A significant difference in favor of the APBI arm in grade ≥ 2 late skin toxicity was observed (p = 0.026). Late toxicity in the breast area (deformation, edema, fibrosis, and pain), affecting the quality of life and cosmetic effect, occurred in 61% and 17% of patients in WBI and APBI arms, respectively. The cosmetic effect was more favorable in the APBI arm, especially 6 to 12 months after the radiotherapy.

CONCLUSION

External APBI demonstrated better feasibility and less toxicity than the standard regimen in the adjuvant setting for treating early breast cancer patients. The presented study confirmed the level of evidence for establishing the external APBI in daily clinical practice.

TRIAL REGISTRATION

NCT06007118.

Comparative evaluation of a surface-based respiratory monitoring system against a pressure sensor for 4DCT image reconstruction in phantoms

Four-dimensional computed tomography (4DCT), which relies on breathing-induced motion, requires realistic surrogate information of breathing variations to reconstruct the tumor trajectory and motion variability of normal tissues accurately. Therefore, the SimRT surface-guided respiratory monitoring system has been installed on a Siemens CT scanner. This work evaluated the temporal and spatial accuracy of SimRT versus our commonly used pressure sensor, AZ-733 V. A dynamic thorax phantom was used to reproduce regular and irregular breathing patterns acquired by SimRT and Anzai. Various parameters of the recorded breathing patterns, including mean absolute deviations (MAD), Pearson correlations (PC), and tagging precision, were investigated and compared to ground-truth. Furthermore, 4DCT reconstructions were analyzed to assess the volume discrepancy, shape deformation and tumor trajectory. Compared to the ground-truth, SimRT more precisely reproduced the breathing patterns with a MAD range of 0.37 ± 0.27 and 0.92 ± 1.02 mm versus Anzai with 1.75 ± 1.54 and 5.85 ± 3.61 mm for regular and irregular breathing patterns, respectively. Additionally, SimRT provided a more robust PC of 0.994 ± 0.009 and 0.936 ± 0.062 for all investigated breathing patterns. Further, the peak and valley recognition were found to be more accurate and stable using SimRT. The comparison of tumor trajectories revealed discrepancies up to 7.2 and 2.3 mm for Anzai and SimRT, respectively. Moreover, volume discrepancies up to 1.71 ± 1.62% and 1.24 ± 2.02% were found for both Anzai and SimRT, respectively. SimRT was validated across various breathing patterns and showed a more precise and stable breathing tracking, (i) independent of the amplitude and period, (ii) and without placing any physical devices on the patient's body. These findings resulted in a more accurate temporal and spatial accuracy, thus leading to a more realistic 4DCT reconstruction and breathing-adapted treatment planning.

Proton Beam Therapy for Breast Cancer

Given the radiobiological and physical properties of the proton, proton beam therapy has the potential to be advantageous for many patients compared with conventional radiotherapy by limiting toxicity and improving patient outcomes in specific breast cancer scenarios.

A Comprehensive Primer on Radiation Oncology for Non-Radiation Oncologists

Background: Multidisciplinary management is crucial in cancer diagnosis and treatment. Multidisciplinary teams include specialists in surgery, medical therapies, and radiation therapy (RT), each playing unique roles in oncology care. One significant aspect is RT, guided by radiation oncologists (ROs). This paper serves as a detailed primer for non-oncologists, medical students, or non-clinical investigators, educating them on contemporary RT practices. Methods: This report follows the process of RT planning and execution. Starting from the decision-making in multidisciplinary teams to the completion of RT and subsequent patient follow-up, it aims to offer non-oncologists an understanding of the RO's work in a comprehensive manner. Results: The first step in RT is a planning session that includes obtaining a CT scan of the area to be treated, known as the CT simulation. The patients are imaged in the exact position in which they will receive treatment. The second step, which is the primary source of uncertainty, involves the delineation of treatment targets and organs at risk (OAR). The objective is to ensure precise irradiation of the target volume while sparing the OARs as much as possible. Various radiation modalities, such as external beam therapy with electrons, photons, or particles (including protons and carbon ions), as well as brachytherapy, are utilized. Within these modalities, several techniques, such as three-dimensional conformal RT, intensity-modulated RT, volumetric modulated arc therapy, scattering beam proton therapy, and intensity-modulated proton therapy, are employed to achieve optimal treatment outcomes. The RT plan development is an iterative process involving medical physicists, dosimetrists, and ROs. The complexity and time required vary, ranging from an hour to a week. Once approved, RT begins, with image-guided RT being standard practice for patient alignment. The RO manages acute toxicities during treatment and prepares a summary upon completion. There is a considerable variance in practices, with some ROs offering lifelong follow-up and managing potential late effects of treatment. Conclusions: Comprehension of RT clinical effects by non-oncologists providers significantly elevates long-term patient care quality. Hence, educating non-oncologists enhances care for RT patients, underlining this report's importance.

Dosimetry impact of distinct gating strategies in cine MR image-guided breath-hold pancreatic cancer radiotherapy

PURPOSE

To investigate the dosimetry effects of different gating strategies in cine magnetic resonance imaging (MRI)-guided breath-hold pancreatic cancer radiotherapy.

METHODS

Two cine MRI-based gating strategies were investigated： a tumor contour-based gating strategy at a gating threshold of 0-5% and a tumor displacement-based gating strategy at a gating threshold of 3-5 mm. The cine MRI videos were obtained from 17 pancreatic cancer patients who received MRI-guided radiation therapy. We calculated the tumor displacement in each cine MR frame that satisfied the gating threshold and obtained the proportion of frames with different displacements. We generated IMRT and VMAT plans using a 33 Gy prescription, and motion plans were generated by adding up all isocenter-shift plans corresponding to different tumor displacements. The dose parameters of GTV, PTV, and organs at risk (OAR) were compared between the original and motion plans.

RESULTS

In both gating strategies, the difference was significant in PTV coverage but not in GTV coverage between the original and motion plans. OAR dose parameters deteriorate with increasing gating threshold. The beam duty cycle increased from 19.5±14.3% (median 18.0%) to 60.8±15.6% (61.1%) for gating thresholds from 0% to 5% in tumor contour-based gating and from 51.7±11.5% (49.7%) to 67.3±12.4% (67.1%) for gating thresholds from 3 to 5 mm in tumor displacement-based gating.

CONCLUSION

In tumor contour-based gating strategy, the dose delivery accuracy deteriorates while the dose delivery efficiency improves with increasing gating thresholds. To ensure treatment efficiency, the gating threshold might be no less than 3%. A threshold up to 5% may be acceptable in terms of the GTV coverage. The displacement-based gating strategy may serve as a potential alternative to the tumor contour based gating strategy, in which the gating threshold of approximately 4 mm might be a good choice for reasonably balancing the dose delivery accuracy and efficiency.

Initial end-to-end testing of the ExacTrac dynamic deep inspiration breath hold workflow using a breath hold breast phantom

ExacTrac Dynamic (ETD) provides a Deep Inspiration Breath Hold (DIBH) workflow for breast patients. Stereoscopic x-ray imaging combined with optical and thermal mapping allows localisation against simulation imaging, alongside surface guided breath hold monitoring. This work aimed to determine appropriate imaging parameters, the optimal Hounsfield Unit (HU) threshold for patient contour generation and workflow evaluation via end-to-end (E2E) positioning using a custom breast DIBH phantom. After localisation via existing Image Guidance (IG), stereoscopic imaging was performed with a range of parameters to determine best agreement. Similarly, residual errors in prepositioning were minimised using a range of HU threshold contours. E2E positioning was completed for clinical workflows allowing residual isocentre position error measurement and existing IG comparison. Parameters of 60 kV and 25mAs were determined appropriate for patient imaging and HU thresholds between -600 HU and -200 HU enabled adequate prepositioning. The average and standard deviation in residual isocentre position error was 1.0 ± 0.9 mm, 0.4 ± 1.0 mm and 0.1 ± 0.5 mm in the lateral, longitudinal and vertical directions, respectively. Errors measured using existing IG were -0.6 ± 1.1 mm, 0.5 ± 0.7 mm and 0.2 ± 0.4 mm in the lateral, longitudinal and vertical directions, and 0.0 ± 1.0o, 0.5 ± 1.7o and -0.8 ± 1.8o for pitch roll and yaw. The use of bone weighted matching increased residual error, while simulated reduction of DIBH volume maintained isocentre positioning accuracy despite anatomical changes. This initial testing indicated suitability for clinical implementation during DIBH breast treatments.

Application of tangent-arc technology for deep inspiration breath-hold radiotherapy in left-sided breast cancer

Objective

To explore the advantages of dosimetry and the treatment efficiency of tangent-arc technology in deep inspiration breath-hold radiotherapy for breast cancer.

Methods

Forty patients with left-sided breast cancer who were treated in our hospital from May 2020 to June 2021 were randomly selected and divided into two groups. The first group's plan was a continuous semi-arc that started at 145° ( ± 5°) and stopped at 325° ( ± 5°). The other group's plan, defined as the tangent-arc plan, had two arcs: the first arc started at 145° ( ± 5°) and stopped at 85° ( ± 5°), and the second arc started at 25° ( ± 5°) and stopped at 325° ( ± 5°). We compared the target dose, dose in organs at risk (OARs), and treatment time between the two groups.

Results

The target dose was similar between the continuous semiarc and tangent-arc groups. The V5 of the right lung was significantly different between the two groups (Dif 5.52, 95% confidence interval 1.92-9.13, t=3.10, P=0.004), with the patients in the continuous semi-arc and tangent-arc groups having lung V5 values of (9.16 ± 1.62)%, and (3.64 ± 0.73)%, respectively. The maximum dose to the spinal cord was (1835.88 ± 222.17) cGy in the continuous semi-arc group and (599.42 ± 153.91) cGy in the tangent-arc group, yielding a significant difference between the two groups (Dif 1236.46, 95% confidence interval 689.32-1783.6, t=4.57, P<0.001). The treatment times was (311.70 ± 60.45) s for patients in the continuous semi-arc group and (254.66 ± 40.73) s for patients in the tangent-arc group, and there was a significant difference in the mean number of treatment times between the two groups (Dif 57.04, 95% confidence interval 24.05-90.03, t=3.5, P=0.001).

Conclusion

Both the continuous semi-arc and tangent-arc plans met the clinical prescription dose requirements. The OARs received less radiation with the tangent-arc plan than the continuous semi-arc plan, especially for the lung (measured as V5) and the spinal cord (measured as the maximum dose). Tangent-arc plan took significantly less time than the continuous semi-arc, which can greatly improve treatment efficiency. Therefore, tangent-arc plans are superior continuous semi-arc plans for all cases.

Advances in Radiotherapy for Breast Cancer

Breast cancer is the most prevalent cancer in women, and the second leading cause of cancer death in women in the United States. Radiation therapy is an important component in the multimodal management of breast cancer, including early stage and locally advanced breast cancers, as well as metastatic cases. Breast cancer radiation therapy has seen significant advancements over the past 20 years. This article discusses the latest advances in the radiotherapeutic management of breast cancer, especially focusing on the technological advances in radiation treatment planning and techniques that have exploited the understanding of radiation biology.

Current Cardioprotective Strategies for the Prevention of Radiation-Induced Cardiotoxicity in Left-Sided Breast Cancer Patients

BACKGROUND

Breast cancer (BC) is the most common malignancy in females, accounting for the majority of cancer-related deaths worldwide. There is well-established understanding about the effective role of radiotherapy (RT) in BC therapeutic strategies, offering a better local-regional control, prolonged survival, and improved quality of life for patients. However, it has been proven that conventional RT modalities, especially in left-sided BC cases, are unable to avoid the administration of high RT doses to the heart, thus resulting in cardiotoxicity and promoting long-term cardiovascular diseases (CVD). Recent radiotherapeutic techniques, characterized by dosimetric dose restrictions, target volume revision/modifications, an increased awareness of risk factors, and consistent follow-ups, have created an advantageous context for a significant decrease inpost-RT CVD incidence.

AIM

This review presents the fundamental role of current cardioprotective strategies in the prevention of cardiotoxic effects in left-BCRT.

MATERIAL AND METHODS

A literature search was conducted up to January 2023 using the Cochrane Central Register of Controlled Trials and PubMed Central databases. Our review refers to new radiotherapeutic techniques carried out on patients after BC surgery. Specifically, a dose evaluation of the heart and left anterior descending coronary artery (LADCA) was pointed out for all the included studies, depending on the implemented RT modality, bed positioning, and internal mammary lymph nodes radiation.

RESULTS

Several studies reporting improved heart sparing with new RT techniques in BC patients were searched. In addition to the RT modality, which definitely determines the feasibility of achieving lower doses for the organs at risk (OARs), better target coverage, dose conformity and homogeneity, and the patient's position, characteristics, and anatomy may also affect the evaluated RT dose to the whole heart and its substructures.

CONCLUSIONS

Modern BC RT techniques seem to enable the administration of lower doses to the OARs without compromising on the target coverage. The analysis of several anatomical parameters and the assessment of cardiac biomarkers potentiate the protective effect of these new irradiation modalities, providing a holistic approach to the radiation-associated risks of cardiac disease for BC patients. Despite technological advances, an inevitable cardiac radiation risk still exists, while adverse cardiac events may be observed even many years after RT. Studies with longer follow-ups are required in order to determine the effectiveness of modern breast RT techniques.

Not Too Little, Not Too Much: Optimizing More Versus Less Locoregional Treatment for Older Patients With Breast Cancer

Although undertreatment of older women with aggressive breast cancers has been a concern for years, there is increasing recognition that some older women are overtreated, receiving therapies unlikely to improve survival or reduce morbidity. De-escalation of surgery may include breast-conserving surgery over mastectomy for appropriate candidates and omitting or reducing extent of axillary surgery. Appropriate patients to de-escalate surgery are those with early-stage breast cancer, favorable tumor characteristics, are clinically node-negative, and who may have other major health issues. De-escalation of radiation includes reducing treatment course length through hypofractionation and ultrahypofractionation regimens, reducing treatment volumes through partial breast irradiation, omission of radiation for select patients, and reducing radiation dose to normal tissues. Shared decision making, which aims to facilitate patients making decisions concordant with their values, can guide health care providers and patients through complicated decisions optimizing breast cancer care.

Differences in radiation-induced heart dysfunction in male versus female rats

PURPOSE

Radiation therapy remains part of the standard of care for breast, lung, and esophageal cancers. While radiotherapy improves local control and survival, radiation-induced heart dysfunction is a common side effect of thoracic radiotherapy. Cardiovascular dysfunction can also result from non-therapeutic total body radiation exposures. Numerous studies have evaluated the relationship between radiation dose to the heart and cardiotoxicity, but relatively little is known about whether there are differences based on biological sex in radiation-induced heart dysfunction (RIHD).

MATERIALS AND METHODS

We evaluated whether male and female inbred Dahl SS rats display differences in RIHD following delivery of 24 Gy in a single fraction to the whole heart using a 1.5 cm beam size (collimater). We also compared the 2.0 cm vs. 1.5 cm collimator in males. Pleural and pericardial effusions and normalized heart weights were measured, and echocardiograms were performed.

RESULTS

Female SS rats displayed more severe RIHD relative to age-matched SS male rats. Normalized heart weight was significantly increased in females, but not in males. A total of 94% (15/16) of males and 55% (6/11) of females survived 5 months after completion of radiotherapy (p < .01). Among surviving rats, 100% of females and 14% of males developed moderate-to-severe pericardial effusions at 5 months. Females demonstrated increased pleural effusions, with the mean normalized pleural fluid volume for females and males being 56.6 mL/kg ± 12.1 and 10.96 mL/kg ± 6.4 in males (p = .001), respectively. Echocardiogram findings showed evidence of heart failure, which was more pronounced in females. Because age-matched female rats have smaller lungs, a higher percentage of the total lung was treated with radiation in females than males using the same beam size. After using a larger 2 cm beam in males which results in higher lung exposure, there was not a significant difference between males and females in terms of the development of moderate-to-severe pericardial effusions or pleural effusions. Treatment of males with a 2 cm beam resulted in comparable increases in LV mass and reductions in stroke volume to female rats treated with a 1.5 cm beam.

CONCLUSION

Together, these results illustrate that there are differences in radiation-induced cardiotoxicity between male and female SS rats and add to the data that lung radiation doses, in addition to other factors, may play an important role in cardiac dysfunction following heart radiation exposure. These factors may be important to factor into future mitigation studies of radiation-induced cardiotoxicity.

Breast Cancer Tumor Board: A Radiologist's Guide to Postmastectomy Radiation Therapy

Radiation therapy represents a pillar in the current management of breast cancer. Historically, postmastectomy radiation therapy (PMRT) has been administered only in patients with locally advanced disease and a poor prognosis. These included patients with large primary tumors at diagnosis and/or more than three metastatic axillary lymph nodes. However, during the past few decades, several factors have prompted a shift in perspective, and recommendations for PMRT have become more fluid. Guidelines for PMRT in the United States are outlined by the National Comprehensive Cancer Network and the American Society for Radiation Oncology. Because evidence to support performing PMRT is frequently discordant, the decision to offer radiation therapy often requires team discussion. These discussions are usually held in multidisciplinary tumor board meetings in which radiologists play a pivotal role by providing critical information such as the location and extent of disease. Breast reconstruction after mastectomy is optional and is safe in cases in which the patient's clinical status allows it. The preferred method in the setting of PMRT is autologous reconstruction. If this is not possible, then a two-step implant-based reconstruction is recommended. Radiation therapy does involve a risk of toxicity. Complications can be seen in acute and chronic settings and range from fluid collections and fractures to radiation-induced sarcomas. Radiologists have a key role in detecting these and other clinically relevant findings and should be prepared to recognize, interpret, and address them. ^© RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Evaluation of the accuracy of a six-degree-of-freedom robotic couch using optical surface and cone beam CT images of an SRS QA phantom

Purpose:

To assess the accuracy of the Varian PerfectPitch six-degree-of-freedom (6DOF) robotic couch by using a Varian SRS QA phantom.

Methods:

The stereotactic radiosurgery (SRS) phantom has five tungsten carbide BBs each with 7·5 mm in diameter arranged with the known geometry. Optical surface images and cone beam CT (CBCT) images of the phantom were taken at different pitch, roll and rotation angles. The pitch, roll, and rotation angles were varied from −3 to 3 degrees by inputs from the linac console. A total of 39 Vision RT images with different rotation angle combinations were collected, and the Vision RT software was used to determine the rotation angles and translational shifts from those images. Eight CBCT images at most allowed rotational angles were analysed by in-house software. The software took the coordinates of the voxel of the maximum CT number inside a 7·5-mm sphere surrounding one BB to be the measured position of this BB. Expected BB positions at different rotation angles were determined by multiplying measured BB positions at zero pitch and roll values by a rotation matrix. Applying the rotation matrix to 5 BB positions yielded 15 equations. A linear least square method was used for regression analysis to approximate the solutions of those equations.

Results:

Of the eight calculations from CBCT images, the maximum rotation angle differences (degree) were 0·10 for pitch, 0·15 for roll and 0·09 for yaw. The maximum translation differences were 0·3 mm in the left–right direction, 0·5 mm in the anterior–posterior direction and 0·4 mm in the superior–inferior direction.

Conclusions:

The uncertainties of the 6-DOF couch were examined with the methods of optical surface imaging and CBCT imaging of the SRS QA phantom. The rotational errors were less than 0·2 degree, and the isocentre shifts were less than 0·8 mm.

Deep Inspiratory Breath-Hold Radiation for Left-Sided Breast Cancer using Novel Frame-based Tactile Feedback

A frame providing tactile feedback for the reproducibility of deep inspiratory breath-hold (DIBH) is described. The frame, fitted across the patient, comprises a horizontal bar, parallel to the patient's long axis, and holds a graduated pointer perpendicular to it. The pointer provides individualized tactile feedback for reproducibility of DIBH. Within the pointer is a movable pencil, bearing a 5 mm coloured strip which becomes visible only during DIBH, and acts as a visual cue to the therapist. The average variation in separation in the planning and pretreatment cone-beam computed tomography of 10 patients was 2 mm (confidence interval 1.95-2.05). Frame-based tactile feedback is a novel, reproducible technique for DIBH.

Feasibility and efficacy of active breathing coordinator assisted deep inspiration breath hold technique for treatment of locally advanced breast cancer

BACKGROUND

Active breathing coordinator (ABC)-assisted deep inspiration breath hold (DIBH) is an important organ sparing radiation therapy (RT) technique for left-sided breast cancer patients. Patients with advanced breast cancer undergoing chest wall and regional nodal irradiation often require a field matching technique. While field matching has been demonstrated to be safe and effective in free breathing patients, its safety and accuracy in DIBH/ABC use has not been previously reported.

PURPOSE

To report the accuracy, feasibility, and safety of field matching with ABC/DIBH for patients receiving breast/chest wall irradiation with nodal irradiation using a three-field technique.

METHODS

From December 2012 to May 2018, breast cancer patients undergoing ABC/DIBH-based RT at a single institution were reviewed. For each fraction, the amount of overlap/gap between the supraclavicular and the tangential field were measured and recorded. Patient characteristics, including acute and delayed skin toxicities, were analyzed.

RESULTS

A total of 202 patients utilized ABC/DIBH and 4973 fractions had gap/overlap measurements available for analysis. The average gap/overlap measured at junction was 0.28 mm ± 0.99 mm. A total of 72% of fractions had no measurable gap/overlap (0 mm), while 5.6% had an overlap and 22.7% a gap. There was no significant trend for worsening or improvement of gap/overlap measurements with increasing fraction number per patient. OSLD measurements were compared to the planned dose. The median dose 1 cm above the junction was 106% ± 7% of planned dose (range 94%-116%). One centimeter below the junction, the median dose was 114% ± 11% of planned dose (range 95%-131%). At the junction, the median dose was 106% ± 16.3% of planned dose (range 86%-131%). Acute skin toxicity was similar to historically reported values (grade 3, 5.4%, grade 4, 0%).

CONCLUSION

ABC-assisted DIBH is a safe and technically feasible method of delivering RT in the setting of complex matching field technique for breast and regional nodal treatments.

A Dosimetric Study Comparing Different Radiotherapy Planning Techniques With and Without Deep Inspiratory Breath Hold for Breast Cancer

Objective

To analyze whether deep inspiratory breath hold (DIBH) would be dosimetrically beneficial irrespective of radiotherapy planning techniques for patients with left breast cancers requiring adjuvant radiotherapy.

Methods

Planning CT scans were taken in free-breathing (FB) as well as deep-inspiration breath hold (DIBH) for patients requiring adjuvant radiotherapy for left breast cancers. After registration, three radiotherapy plans - 3D-conformal radiotherapy (3DCRT), intensity modulated RT (IMRT), and volumetric modulated arc-therapy (VMAT) - were generated for both FB and DIBH scans for each patient. The dose-volume parameters were collected from the dose-volume histogram and analyzed. A paired t-test is used for statistical analysis of the parameters.

Findings

The study was conducted on thirteen patients. The mean dose of the left lung was reduced with DIBH by 32%, 24%, and 6% (8.6 Gy, 6.6 Gy, and 6.4 Gy) with 3DCRT, IMRT, and VMAT, respectively. The mean heart dose was reduced by 3.3 Gy (2.2 vs 5.5 Gy), 2.2 Gy (7.5 vs 9.7 Gy), and 1.2 Gy (5.8 vs 7 Gy) with 3DCRT, IMRT, and VMAT with DIBH. Similarly, the left anterior descending artery (LAD) mean dose was relatively reduced by 80%, 34%, and 20% when compared with the FB scans for 3DCRT, IMRT, and VMAT respectively, with max dose in the 3DCRT plan.

Novelty/Applications

DIBH appears to have maximum benefit in achieving a better sparing of organs-at-risk for patients being considered for 3DCRT, and to a lesser extent with even IMRT and VMAT techniques.

Deep inspiratory breath-hold radiotherapy for left-sided breast cancer: Initial experience with Active Breathing Coordinator™ in a regional hospital

INTRODUCTION

Deep inspiratory breath-hold (DIBH) has become standard in radiotherapy for left-sided breast cancer to reduce the heart dose. This study evaluated breath-hold stability and reproducibility using Elekta's Active Breathing Coordinator™ (ABC) and its effectiveness and feasibility in left-sided breast cancer patients undergoing radiotherapy.

METHODS

Eligible patients were planned with free breathing (FB) and DIBH protocols. DIBH treatment was considered if the mean heart dose (MHD) was ≥2 Gy on the FB plan. Those who proceeded with DIBH treatment were enrolled for the pilot study. Electronic portal images of DIBH treatment beams were taken using the movie-exposure mode for breath-hold stability and reproducibility analysis. DIBH effectiveness in heart dose reduction and impact on simulation and treatment durations were compared with FB protocol.

RESULTS

Out of 56 eligible patients, 15 proceeded with DIBH treatment. The mean difference of patient setup within a single breath-hold was 0.4 mm; between different breath-holds of the same beam 1.1 mm and between different days 2.6 mm. DIBH reduced the MHD by 47% and the mean left anterior descending artery (LAD) dose by 35%. DIBH took longer time than FB in simulation and treatment. At least 14% of the eligible patients did not tolerate DIBH during simulation.

CONCLUSIONS

ABC leads to stable and reproducible breath-holds and results in significant heart dose reductions. It may not be tolerated by all patients and has resource implications.

Cardiovascular Disease in Adult Cancer Survivors: a Review of Current Evidence, Strategies for Prevention and Management, and Future Directions for Cardio-oncology

PURPOSE OF REVIEW

Cardiovascular disease is long-term complication of both cancer and anti-cancer treatment and can have significant ramifications for health-related quality of life and mortality. This narrative review explores the current evidence linking cardiovascular disease and cancer, as well as exploring strategies for the prevention and management of cardiovascular disease, and outlines future opportunities in the field of cardio-oncology.

RECENT FINDINGS

Cancer confers risk for various cardiovascular diseases including heart failure, cardiomyopathy, arrhythmia, coronary heart disease, stroke, venous thromboembolism, and valvular heart disease. Cancer treatment, in particular agents such as platinum-based chemotherapy, anthracyclines, hormonal treatments, and thoracic radiotherapy, further increases risk. While cardiovascular disease can be identified early and effectively managed in cancer survivors, cardiovascular screening and management does not typically feature in routine long-term cancer care of adult cancer survivors. Cancer and cancer treatment can accelerate the development of cardiovascular disease. Further research into screening and management strategies for cardiovascular disease, along with evidence-based guidelines, is required to ensure adult cancer survivors receive appropriate long-term care.

Retrospective Analysis for Dose Reduction to Organs at Risk with New Personalized Breast Holder (PERSBRA) in Left Breast IMRT

This study evaluated dose differences in normal organs at risk, such as the lungs, heart, left anterior descending artery (LAD), right coronary artery, left ventricle, and right breast under personalized breast holder (PERSBRA), when using intensity-modulated radiation therapy (IMRT). This study evaluated the radiation protection offered by PERSBRA in left breast cancer radiation therapy. Here, we retrospectively collected data from 24 patients with left breast cancer who underwent breast-conserving surgery as well as IMRT radiotherapy. We compared the dose differences in target coverage and organs at risk with and without PERSBRA. For target coverage, tumor prescribed dose 95% coverage, conformity index, and homogeneity index were evaluated. For organs at risk, we compared the mean heart dose, mean left ventricle dose, LAD maximum and mean dose, mean left lung receiving 20 Gy, 10 Gy, and 5 Gy of left lung volume, maximum and mean coronary artery of the right, maximum of right breast, and mean dose. Good target coverage was achieved with and without PERSBRA. When PERSBRA was used with IMRT, the mean dose of the heart decreased by 42%, the maximum dose of LAD decreased by 26.4%, and the mean dose of LAD decreased by 47.0%. The mean dose of the left ventricle decreased by 54.1%, the volume (V₂₀) of the left lung that received 20 Gy decreased by 22.8%, the volume (V₁₀) of the left lung that received 10 Gy decreased by 19.8%, the volume (V₅) of the left lung that received 5 Gy decreased by 15.7%, and the mean dose of the left lung decreased by 23.3%. Using PERSBRA with IMRT greatly decreases the dose to organs at risk (left lung, heart, left ventricle, and LAD). This study found that PERSBRA with IMRT can achieve results similar to deep inspiration breath-hold radiotherapy (DIBH) in terms of reducing the heart radiation dose and the risk of developing heart disease in patients with left breast cancer who cannot undergo DIBH.

Inter-fraction heart displacement during voluntary deep inspiration breath hold radiation therapy without visual feedback measured by daily CBCT

Purpose/Objective

Deep Inspiration Breath Hold (DIBH) is now considered as the standard of care for many breast cancer patients. However, there are still uncertainties about the dose given to the heart, and it is unknown if patients may improve voluntary DIBH depth by gaining experience during treatment. In this study, we will examine the interfractional three-dimensional (3D) heart displacement throughout voluntary DIBH (vDIBH) radiotherapy by means of daily cone-beam computed tomography (CBCT).

Material and methods

Two hundred twenty-five unique CBCTs from 15 patients treated in 15 fractions were analyzed. During CBCT, a vDIBH was conducted without any visual feedback. Patients performed their DIBH freely after receiving explanations and training. After daily CBCT matching to the chest wall (CW), surface-guided radiation therapy (SGRT) tracked DIBH depth to ensure that the CW position was the same as the daily acquired CBCT. The CBCTs were retrospectively registered to the DIBH planning-CT to calculate daily changes in heart displacement relative to the CW.

Results

The mean displacement of the heart during DIBH treatment relative to the DIBH planning-CT was as follows: 1.1 mm to the right, interquartile range (IQR) 8.0; 0.5 mm superiorly, IQR 4.8; and 0 mm posteriorly, IQR 6.4. The Spearman correlation coefficients (r_s) were -0.15 (p=0.025), 0.04 (p=0.549), and 0.03 (p=0.612) for the X, Y, and Z directions, respectively. The differences in median heart displacement were significant: Friedmann rank sum test p=0.031 and pairwise comparison using the Wilcoxon rank-sum test were p=0.008 for X and Y; p=0.33 for X and Z; and p=0.07 for Y and Z. The total median heart motion was δ_{tot median}= 7.26 mm, IQR= 6.86 mm.

Conclusion

During DIBH, clinicians must be aware of the wide range of intra- and inter-individual heart position variations. The inter-individual heterogeneity shown in our study should be investigated further in order to avoid unexpected cardiac overexposure and to develop a more accurate heart dose-volume model.