Reducing cardiac doses: a novel multi-leaf collimator modification technique to reduce left anterior descending coronary artery dose in patients with left-sided breast cancer

Heart and Coronary Artery Dose Sparing in Left-sided Breast Cancer: 3D-Conformal Radiotherapy vs. Helical Tomotherapy

BACKGROUND/AIM

To compare heart, left ventricle (LV) and coronary artery dose-sparing with three-dimensional conformal radiotherapy (3D-CRT) vs. helical tomotherapy (HT) in left-sided breast cancer (BC).

PATIENTS AND METHODS

3D-CRT and HT treatments were planned for 20 patients (pts). Computed tomography (CT) scans without and with intravenous contrast (ic) were performed and co-registered. Left breast and organs at risk (OARs) were contoured. Dose-volume histograms (DVHs) for 3D-CRT and HT treatment plans were evaluated in terms of planning target volume for evaluation (PTVeval) coverage and dose to the OARs.

RESULTS

HT provided the best target coverage and significantly reduced D2% and mean dose to the left anterior descending artery (LADA) and to the LADA-planning organ at risk volume (PRV), D2%, V5 and mean dose to the LV and D2% and V25 to the heart. As expected, due to the rotational delivery, the dose to all other coronary arteries and their PRV, contralateral breast and lungs was higher with HT.

CONCLUSION

In left-sided BC, HT provided the best target coverage and significantly reduced LV and LADA doses. Moreover D2% and V25 to the heart were significantly reduced. Further studies are needed to correlate dosimetric findings with in-depth cardiac monitoring.

Cardiotoxicity in breast cancer treatment: Causes and mitigation

Survivorship issues and treatment related toxicities have considerably increased in breast cancer patients following improved therapeutic options. Cardiotoxicity has been a major treatment related side effects in these patients. Despite this being a well-known entity, the real magnitude of the problem remains an enigma. The amount of research in mitigation of cardiotoxicity or its management in breast cancer survivors is limited and there is an urgent need for finding solutions for the problem. In this article, we are reviewing the agents that cause cardiotoxicity and suggesting a proposal for follow up of breast cancer survivors in an attempt to reduce the magnitude of impact on their quality of life.

The Efficacy of Multi-Leaf Collimator in the Reduction of Cardiac and Coronary Artery Dose in Left-Sided Breast Cancer Radiotherapy

Background

Multi-leaf collimator (MLC) is one of the efficient and cost-effective methods for protecting sensitive tissues around the target. This study aimed to evaluate the protective effect of MLC on the protection of sensitive organs in patients with left breast cancer.

Materials and Methods

This study was performed on computed tomography (CT) scans of 45 patients with left breast cancer. Two treatment plans were completed for each patient. Only the heart and left lung were considered organs at risk in the first treatment plan, and in the second treatment plan, the left anterior descending artery (LAD) was also considered the organ at risk. It was covered as much as possible by the MLC. Dosimetric results of tumor and organ at risk (OARs) were extracted from the dose-volume histogram and compared.

Results

The results showed that more LAD coverage by MLC leads to a significant reduction in the mean dose of OARs (P-value <0.05). The mean dose for heart, LAD, and left lung decreased by 11%, 7.4%, and 4.9%, respectively. The values of V₅ (volume received the dose of 5 Gy) and V₂₀ for the lung, V₁₀, V₂₅, and V30 for LAD, and V₅, V₂₀, V₂₅, and V₃₀ for the heart also decreased significantly (P-value <0.05).

Conclusions

In general, better protection of LAD, heart, and lungs can be achieved by maximal shielding organs at risk by MLC in radiation therapy for patients with left breast cancer.

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

Introduction

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

Materials and Methods

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

Results

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

Conclusion

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

Radiation-Induced Cardiovascular Disease: Mechanisms, Prevention, and Treatment

PURPOSE OF REVIEW

Despite the advancements of modern radiotherapy, radiation-induced cardiovascular disease (RICVD) remains a common cause of morbidity and mortality among cancer survivors.

RECENT FINDINGS

Proposed pathogenetic mechanisms of RICVD include endothelial cell damage with accelerated atherosclerosis, pro-thrombotic alterations in the coagulation pathway as well as inflammation and fibrosis of the myocardial, pericardial, valvular, and conduction tissues. Prevention of RICVD can be achieved by minimizing the exposure of the cardiovascular system to radiation, by treatment of underlying cardiovascular risk factors and cardiovascular disease, and possibly by prophylactic pharmacotherapy post exposure. Herein we summarize current knowledge on the mechanisms underlying the pathogenesis of RICVD and propose prevention and treatment strategies.

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

PURPOSE

Our institution introduced a patient-specific heart constraint (PSHC) and a mean heart dose (MHD) constraint of 4 Gy for all patients receiving breast radiation therapy (RT) with a simultaneous boost (SIB). This was introduced as a method to calculate the predicted MHD before optimizing IMRT fields. We sought to determine whether the introduction of a PSHC reduced MHD, while maintaining optimally dosed treatment plans.

MATERIAL/METHODS

Patients were retrospectively divided into 2 groups, pre- and postintroduction of the PSHC. The breast and SIB Planning Target Volumes (PTVs) were prescribed to 50 Gy and 57 Gy, respectively, in 25 fractions. Plans were generated using a hybrid IMRT technique, 30 Gy using an open tangential field arrangement, and 27 Gy using IMRT fields. The PSHC was calculated using MHD of open tangential field × 2. A paired t test compared PTV coverage and heart doses between cohorts (P < .05 significant).

RESULTS

A total of 264 patients were included (138 pre-PSHC and 126 post-PSHC) with 137 right-sided and 127 left-sided treatments. MHD was significantly reduced across both right-sided (-0.4 Gy, P < .0001) and left-sided (-1.2 Gy, P < .0001) treatments overall. Left-sided treatments were further examined between free breathing and deep inspiration breath-hold (DIBH). DIBH showed reduction in MHD, although it was not significant (-0.46 Gy, P = .34). Heart V5 Gy showed reduction in right-sided (-1%, P = .002) and left-sided (-9.2%, P < .0001) treatments overall. Left-sided free breathing showed significant reduction (-8.8%, P < .0001), and DIBH also showed significant reduction (-5.1%, P = .0034). Tumor bed doses remained above the 54.15 Gy (95% of 57 Gy) threshold for all plans.

CONCLUSION

Introduction of a PSHC can reduce MHD and V5 Gy for patients receiving whole breast RT with SIB while maintaining optimally dosed plans, with the greatest benefit shown for left-sided, free-breathing treatments.

Modern Radiotherapy and Risk of Cardiotoxicity

Despite the advancements of modern radiotherapy, radiation-induced heart disease remains a common cause of morbidity and mortality amongst cancer survivors. This review outlines the basic mechanism, clinical presentation, risk stratification, early detection, possible mitigation, and treatment of this condition.

Outcomes of percutaneous coronary interventions in cancer patients

Introduction: There are numerous shared risk factors in the etiopathogenesis of coronary artery disease (CAD) and cancer both at epidemiologic and molecular level. Additionally, different modalities of treatment of cancer such as radiation, chemotherapy, immunotherapy, and hormonal therapies further increase the risk of CAD and acute coronary syndrome. Most large database analysis and single-center experiences have shown that cancer patients undergoing PCI are at an increased risk of in-hospital mortality, bleeding, repeat revascularization.Areas covered: In this review article the authors discuss the associations between CAD and cancer, challenges for PCI in cancer patients and outcome data.Expert opinion: Interventionists performing PCI on cancer patients should be cognizant of the heightened risk of bleeding, thrombosis, possible need for interruption of dual-antiplatelet therapy, and the increased risk of target lesion revascularization in this cohort. These risks may be partially mitigated by utilization of best practices such as the use of radial artery access, intravascular imaging for lesion assessment and stent optimization and avoidance of complex stenting strategies. Finally, it is of paramount importance to have a multidisciplinary approach consisting of the treating cardiologist, medical and/or surgical oncologist, and palliative medicine, and involve the patient and their family in making informed decisions.

Evaluating a potential technique with local optical flow vectors for automatic organ-at-risk (OAR) intrusion detection and avoidance during radiotherapy

Various techniques of deep inspiration breath hold (DIBH) have been used to mitigate the likelihood and risk of exposing the heart, an organ-at-risk (OAR) for unintended radiation during left breast radiotherapy. However, issues of reproducibility of these techniques warrant further investigation into the feasibility of detecting the intrusion of an OAR into the treatment field during intra-fractional treatment delivery. The increase of high-dose, low-fraction radiotherapy treatments makes it important to immediately adapt treatment once an OAR is detected in the treatment field. This proof-of-concept implementation includes an algorithm that detects and tracks the motion at the edges of a treatment field and a control algorithm that adapts the treatment aperture according to the motion detected. In accordance to the AAPM Task-Group (TG-132) report, image registration techniques should be verified with virtual and physical phantoms prior to clinical application. Since most OARs move as a result of respiration-induced motion, we have used a lung phantom to generate images of a generic OAR intruding into a treatment field with known velocity. The phantom was programmed to move with sinusoidal and lung patient tumor motion patterns and the accuracy of intrusion tracking and MLC adaptation were benchmarked with the ground truth-programmed motion of the OAR. The motions were recorded with an electronic portal imaging device (EPID). An optimal cluster size of 9  ×  9 motion vectors was found to provide the smallest average absolute position error of 0.3 mm. A strong linear correlation between the adapted MLC leaves and the actual OAR position was observed. The algorithm had a mean position tracking error of  -0.4  ±  0.3 mm and a precision of 1.1 mm. It is possible to adapt MLC leaves based on the motion detected at the edges of the irradiated field, and it would be feasible to shield an unplanned intrusion of an OAR into the treatment field.

Reducing cardiac doses: a novel multi-leaf collimator modification technique to reduce left anterior descending coronary artery dose in patients with left-sided breast cancer

Introduction

When irradiating the left breast, a small portion of the heart and left anterior descending coronary artery (LAD) are often included in the treatment field. Deep inspiration breath‐hold (DIBH) techniques reduce dose to coronary structures, but are resource intensive and may not be tolerated by all patients. The aim of this study was to evaluate a simple multi‐leaf collimator (MLC) modification technique with respect to target coverage and organ‐at‐risk sparing.

Methods

Forty nine patients with left‐sided breast cancer, planned with a simultaneous integrated boost technique were retrospectively replanned with additional shielding of the LAD. Dose to the target volumes (whole breast and boost) and organs at risk (heart, ipsilateral lung and LAD) were assessed on both plans.

Results

Significant dose reductions were observed for all organs at risk when LAD shielding was introduced, with a reduction in mean LAD dose of 7.0 Gy, mean LAD planning risk volume (PRV) dose of 5.9 Gy, maximum LAD dose of 12 Gy and mean heart dose of 0.73 Gy. Target volume coverage was clinically acceptable for 96% of patients, using the left anterior descending coronary artery shielded plan (LADSP). No difference was observed between the standard plan (SP) and LADSP in nine patients (18%).

Conclusions

For selected patients, the implementation of a simple MLC shielding technique can reduce the dose to cardiac structures, whilst maintaining breast and boost volume dosimetry. This technique is simple to implement and may be used as an alternative to DIBH for those patients who are unable to fulfill the selection criteria, or departments who are not resourced to perform DIBH.