Impact of patient-specific factors, irradiated left ventricular volume, and treatment set-up errors on the development of myocardial perfusion defects after radiation therapy for left-sided breast cancer

Hypofractionated Stereotactic Radiation Therapy Dosimetric Tolerances for the Inferior Aspect of the Brachial Plexus: A Systematic Review

We sought to systematically review and summarize dosimetric factors associated with radiation-induced brachial plexopathy (RIBP) after stereotactic body radiation therapy (SBRT) or hypofractionated image guided radiation therapy (HIGRT). From published studies identified from searches of PubMed and Embase databases, data quantifying risks of RIBP after 1- to 10-fraction SBRT/HIGRT were extracted and summarized. Published studies have reported <10% risks of RIBP with maximum doses (Dmax) to the inferior aspect of the brachial plexus of 32 Gy in 5 fractions and 25 Gy in 3 fractions. For 10-fraction HIGRT, risks of RIBP appear to be low with Dmax < 40 to 50 Gy. For a given dose value, greater risks are anticipated with point volume-based metrics (ie, D0.03-0.035cc: minimum dose to hottest 0.03-0.035 cc) versus Dmax. With SBRT/HIGRT, there were insufficient published data to predict risks of RIBP relative to brachial plexus dose-volume exposure. Minimizing maximum doses and possibly volume exposure of the brachial plexus can reduce risks of RIBP after SBRT/HIGRT. Further study is needed to better understand the effect of volume exposure on the brachial plexus and whether there are location-specific susceptibilities along or within the brachial plexus structure.

Nuclear medicine imaging methods of early radiation-induced cardiotoxicity: a ten-year systematic review

Introduction

Radiotherapy has significantly improved cancer survival rates, but it also comes with certain unavoidable complications. Breast and thoracic irradiation, for instance, can unintentionally expose the heart to radiation, leading to damage at the cellular level within the myocardial structures. Detecting and monitoring radiation-induced heart disease early on is crucial, and several radionuclide imaging techniques have shown promise in this regard.

Method

In this 10-year review, we aimed to identify nuclear medicine imaging modalities that can effectively detect early cardiotoxicity following radiation therapy. Through a systematic search on PubMed, we selected nineteen relevant studies based on predefined criteria.

Results

The data suggest that incidental irradiation of the heart during breast or thoracic radiotherapy can cause early metabolic and perfusion changes. Nuclear imaging plays a prominent role in detecting these subclinical effects, which could potentially serve as predictors of late cardiac complications.

Discussion

However, further studies with larger populations, longer follow-up periods, and specific heart dosimetric data are needed to better understand the relationship between early detection of cardiac abnormalities and radiation-induced heart disease.

Changes in myocardial blood flow in a canine model of left sided breast cancer radiotherapy

BACKGROUND

Left-sided breast cancer patients receiving adjuvant radiotherapy are at risk for coronary artery disease, and/or radiation mediated effects on the microvasculature. Previously our laboratory demonstrated in canines with hybrid 18FDG/PET a progressive global inflammatory response during the initial one year following treatment. In this study, the objective is to evaluate corresponding changes in perfusion, in the same cohort, where resting myocardial blood flow (MBF) was quantitatively measured.

METHOD

In five canines, Ammonia PET (13NH3) derived MBF was measured at baseline, 1-week, 1, 3, 6 and 12-months after cardiac external beam irradiation. MBF measurements were correlated with concurrent 18FDG uptake. Simultaneously MBF was measured using the dual bolus MRI method.

RESULTS

MBF was significantly increased at all time points, in comparison to baseline, except at 3-months. This was seen globally throughout the entire myocardium independent of the coronary artery territories. MBF showed a modest significant correlation with 18FDG activity for the entire myocardium (r = 0.51, p = 0.005) including the LAD (r = 0.49, p = 0.008) and LCX (r = 0.47, p = 0.013) coronary artery territories.

CONCLUSION

In this canine model of radiotherapy for left-sided breast cancer, resting MBF increases as early as 1-week and persists for up to one year except at 3-months. This pattern is similar to that of 18FDG uptake. A possible interpretation is that the increase in resting MBF is a response to myocardial inflammation.

Integrating subvolume dose and myocardial perfusion imaging parameters to assess the impact of radiation therapy on heart function in breast cancer patients: A comparative analysis between left- and right-sided breast cancer

BACKGROUND

This study aimed to utilize an innovative method of integrating the 20 subvolume dose of left ventricle and the Tl-201 single photon emission computed tomography (SPECT) with myocardial perfusion imaging (MPI) parameters in patients with left- and right-sided breast cancer after radiation therapy.

METHODS

Female patients with breast cancer underwent SPECT MPI before commencing radiotherapy and 12 months later were enrolled from January 2014 to December 2018. The images of CT simulation and SPECT MPI were integrated into the treatment planning system. The differences of doses and parameters of MPI in all cardiac subvolumes between left- and right-sided breast cancer patients were analyzed.

RESULTS

Patients with left-sided breast cancer (n = 61) received a higher radiation dose to the heart, left ventricular, and its territories and subvolumes, compared to patients with right-sided breast cancer (n = 19). The 20-segment analysis also showed statistically significant disparities in the average radiation doses received by the two groups. In different coronary artery territories, the end-diastolic perfusion and end-systolic perfusion showed a decrease in both sides, with no significant differences. However, the wall motion and wall thickening showed a significant decline in subregions within the left- and right-sided coronary artery territories.

CONCLUSION

This study demonstrates an innovative integrated method combining the left ventricular 20 regional doses with SPECT MPI which shows that left-sided breast cancer patients receive a higher subvolume dose than right-sided breast cancer patients. Further research is needed to confirm the potential impact on heart function after radiotherapy on both sides.

Dosimetric Evaluation of Cardiac Structures on Left Breast Cancer Radiotherapy: Impact of Movement, Dose Calculation Algorithm and Treatment Technique

BACKGROUND

Breast cancer is the most frequently diagnosed and leading cause of cancer-related deaths among females. The treatment of breast cancer with radiotherapy, albeit effective, has been shown to be toxic to the heart, resulting in an elevated risk of cardiovascular disease and associated fatalities.

METHODS

In this study, we evaluated the impact of respiratory movement, treatment plans and dose calculation algorithm on the dose delivered to the heart and its substructures during left breast radiotherapy over a cohort of 10 patients. We did this through three image sets, four different treatment plans and the employment of three algorithms on the same treatment plan. The dose parameters were then employed to estimate the impact on the 9-year excess cumulative risk for acute cardiac events by applying the model proposed by Darby.

RESULTS

The left ventricle was the structure most irradiated. Due to the lack of four-dimensional computed tomography (4DCT), we used a set of images called phase-average CT that correspond to the average of the images from the respiratory cycle (exhale, exhale 50%, inhale, inhale 50%). When considering these images, nearly 10% of the heart received more than 5 Gy and doses were on average 27% higher when compared to free breathing images. Deep inspiration breath-hold plans reduced cardiac dose for nine out of 10 patients and reduced mean heart dose in about 50% when compared to reference plans. We also found that the implementation of deep inspiration breath-hold would reduce the relative lifetime risk of ischemic heart disease to 10%, in comparison to 21% from the reference plan.

CONCLUSION

Our findings illustrate the importance of a more accurate determination of the dose and its consideration in cardiologists' consultation, a factor often overlooked during clinical examination. They also motivate the evaluation of the dose to the heart substructures to derive new heart dose constraints, and a more mindful and individualized clinical practice depending on the treatment employed.

[Impact of adapted physical activity on joint pain induced under adjuvant hormone therapy for breast cancer: A review of the literature]

Hormone therapy provides an excellent survival rate after cancer but has many side effects, including joint pain in one out of two women. This leads about 13 % of women to stop their treatment within the first 6 months, impacting on its effectiveness, survival and the risk of recurrence. In order to better manage pain and quality of life, physical activity is highly recommended. In this context, the present review proposes a state of the art on the effects of adapted physical activity, based on the works referenced in PubMed. These studies show that physical activity has proved its worth in the primary prevention of cancer and is being evaluated in secondary prevention, particularly in the reduction of adverse effects. Overall, there is a reduction in joint pain, an improvement in quality of life and fatigue. Physical activity also plays a role in tertiary prevention. Paradoxically, oncologists and educators often note a reduction in the practice of physical activity due to fear of the onset of pain. It seems necessary to reinforce communication with patients and health professionals and to recommend the practice of physical activity in an appropriate setting.

Heart Sparing Radiotherapy Techniques in Breast Cancer: A Focus on Deep Inspiration Breath Hold

Adjuvant radiation therapy is a critical component of breast cancer management. However, when breast cancer patients receive incidental radiation to the heart, there is an increased risk of cardiac disease and mortality. This is most common for patients with left-sided breast cancers and those receiving nodal irradiation as part of treatment. The overall risk of cardiac toxicity increases 4–16% with each Gray increase in mean heart radiation dose, with data suggesting that no lower limit exists which would eliminate cardiac risk entirely. Radiation techniques have improved over time, leading to lower cardiac radiation exposure than in the past. This decline is expected to reduce the incidence of radiation-induced heart dysfunction in patients. Deep inspiration breath hold (DIBH) is one such technique that was developed to reduce the risk of cardiac death and coronary events. DIBH is a non-invasive approach that capitalizes on the natural physiology of the respiratory cycle to increase the distance between the heart and the therapeutic target throughout the course of radiation therapy. DIBH has been shown to decrease the mean incidental radiation doses to the heart and left anterior descending coronary artery by approximately 20–70%. In this review, we summarize different techniques for DIBH and discuss recent data on this technique.

A Pilot Study of Cardiac MRI in Breast Cancer Survivors After Cardiotoxic Chemotherapy and Three-Dimensional Conformal Radiotherapy

PURPOSE/OBJECTIVES

Node-positive breast cancer patients often receive chemotherapy and regional nodal irradiation. The cardiotoxic effects of these treatments, however, may offset some of the survival benefit. Cardiac magnetic resonance (CMR) is an emerging modality to assess cardiac injury. This is a pilot trial assessing cardiac damage using CMR in patients who received anthracycline-based chemotherapy and three-dimensional conformal radiotherapy (3DCRT) regional nodal irradiation using heart constraints.

MATERIALS AND METHODS

Node-positive breast cancer patients (2000-2008) treated with anthracycline-based chemotherapy and 3DCRT regional nodal irradiation (including the internal mammary chain nodes) with heart ventricular constraints (V25 < 10%) were invited to participate. Cardiac tissues were contoured and analyzed separately for whole heart (pericardium) and for combined ventricles and left atrium (myocardium). CMR obtained ventricular function/dimensions, late gadolinium enhancement (LGE), global longitudinal strain (GLS), and extracellular volume fraction (ECV) as measures of cardiac injury and/or early fibrosis. CMR parameters were correlated with dose-volume constraints using Spearman correlations.

RESULTS

Fifteen left-sided and five right-sided patients underwent CMR. Median diagnosis age was 50 (32-77). No patients had baseline cardiac disease before regional nodal irradiation. Median time after 3DCRT was 8.3 years (5.2-14.4). Median left-sided mean heart dose (MHD) was 4.8 Gy (1.1-11.2) and V25 was 5.7% (0-12%). Median left ventricular ejection fraction (LVEF) was 63%. No abnormal LGE was observed. No correlations were seen between whole heart doses and LVEF, LV mass, GLS, or LV dimensions. Increasing ECV did not correlate with increased heart or ventricular doses. However, correlations between higher LV mass and ventricular mean dose, V10, and V25 were seen.

CONCLUSION

At a median follow-up of 8.3 years, this cohort of node-positive breast cancer patients who received anthracycline-based chemotherapy and regional nodal irradiation had no clinically abnormal CMR findings. However, correlations between ventricular mean dose, V10, and V25 and LV mass were seen. Larger corroborating studies that include advanced techniques for measuring regional heart mechanics are warranted.

Comparison of the dose on specific 3DCT images and the accumulated dose for cardiac structures in esophageal tumors radiotherapy: whether specific 3DCT images can be used for dose assessment?

BACKGROUND

Cardiac activity could impact the accuracy of dose assessment for the heart, pericardium and left ventricular myocardium (LVM). The purpose of this study was to explore whether it is possible to perform dose assessment by contouring the cardiac structures on specific three-dimensional computed tomography (3DCT) images to reduce the impact of cardiac activity.

METHODS

Electrocardiograph-gated 4DCT (ECG-gated 4DCT) images of 22 patients in breath-hold were collected. MIM Maestro 6.8.2 (MIM) was used to reconstruct specific 3DCT images to obtain the Maximal intensity projection (MIP) image, Average intensity projection (AIP) image and Minimum intensity projection (Min-IP) image. The heart, pericardium and LVM were contoured in 20 phases of 4DCT images (0, 5%... 95%) and the MIP, AIP and Min-IP images. Then, a radiotherapy plan was designed at the 0% phase of the 4DCT images, and the dose was transplanted to all phases of 4DCT to acquire the dose on all phases, the accumulated dose of all phases was calculated using MIM. The dose on MIP, AIP and Min-IP images were also obtained by deformable registration of the dose. The mean dose (D_mean), V₅, V₁₀, V₂₀, V₃₀ and V₄₀ for the heart, pericardium and LVM in MIP, AIP and Min-IP images were compared with the corresponding parameters after dose accumulation.

RESULTS

The mean values of the difference between the D_mean in the MIP image and the D_mean after accumulation for the heart, pericardium and LVM were all less than 1.50 Gy, and the dose difference for the pericardium and LVM was not statistically significant (p > 0.05). For dose-volume parameters, there was no statistically significant difference between V₅, V₁₀, and V₂₀ of the heart and pericardium in MIP, AIP, and Min-IP images and those after accumulation (p > 0.05). For the LVM, only in the MIP image, the differences of V₅, V₁₀, V₂₀, V₃₀ and V₄₀ were not significant compared to those after dose accumulation (p > 0.05).

CONCLUSIONS

There was a smallest difference for the dosimetry parameters of cardiac structures on MIP image compared to corresponding parameters after dose accumulation. Therefore, it is recommended to use the MIP image for the delineation and dose assessment of cardiac structures in clinical practice.

Efficacy of Dexrazoxane in Preventing Anthracycline Cardiotoxicity in Breast Cancer

Objectives

The authors performed a systematic review and meta-analysis of randomized and nonrandomized trials on the efficacy of dexrazoxane in patients with breast cancer who were treated with anthracyclines with or without trastuzumab.

Background

Breast cancer treatment with anthracyclines and trastuzumab is associated with an increased risk of cardiotoxicity. Among the various strategies to reduce the risk of cardiotoxicity, dexrazoxane is an option for primary prevention, but it is seldom used in clinical practice.

Methods

Online databases were searched from January 1990 up to March 1, 2019, for clinical trials on the use of dexrazoxane for the prevention of cardiotoxicity in patients with breast cancer receiving anthracyclines with or without trastuzumab. Risk ratios (RRs) with 95% confidence intervals (CIs) were calculated using a random-effects model meta-analysis.

Results

Seven randomized trials and 2 retrospective trials with a total of 2,177 patients were included. Dexrazoxane reduced the risk of clinical heart failure (RR: 0.19; 95% CI: 0.09 to 0.40; p < 0.001) and cardiac events (RR: 0.36; 95% CI: 0.27 to 0.49; p < 0.001) irrespective of previous exposure to anthracyclines. The rate of a partial or complete oncological response, overall survival, and progression-free survival were not affected by dexrazoxane.

Conclusions

Dexrazoxane reduced the risk of clinical heart failure and cardiac events in patients with breast cancer undergoing anthracycline chemotherapy with or without trastuzumab and did not significantly impact cancer outcomes. However, the quality of available evidence is low, and further randomized trials are warranted before the systematic implementation of this therapy in clinical practice.

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

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

15O-H2O PET/CT as a tool for the quantitative assessment of early post-radiotherapy changes of heart perfusion in breast carcinoma patients

OBJECTIVE

Studies examining radiation-induced heart toxicity in breast cancer patients are inconclusive. The aim of this study was to prospectively and quantitatively asses myocardial blood flow (MBF) with, for the first time, ¹⁵O-H₂O PET/CT as a marker of heart damage in irradiated breast cancer patients.

METHODS

15 breast cancer patients receiving intact breast or chest wall irradiation were included in the analysis (six with right-sided and nine with left-sided breast cancer). They underwent ¹⁵O-H₂O PET/CT before radiotherapy (RT) and 2 and 8 months after RT. MBF was quantitatively assessed at rest and under stress conditions in 17 heart segments distinguished according to the American Ultrasound Association classification. Regional MBF values were derived in each of the coronary artery territories.

RESULTS

MBF decreased in 53% and increased in 33% of cases 2 months after RT in both left-sided and right-sided breast cancer patients. Stress testing was more sensitive than at-rest testing, demonstrating decreased perfusion in the segments supplied by the left anterior descending coronary artery (LAD) [5.41 ± 1.74 vs 4.52 ± 1.82 ml (g*min)^-1; p = 0.018], which persisted at 6 months [5.41 ± 1.74 vs 4.40 ± 1.38 ml (g*min)^-1; p = 0.032] and a decrease in global heart perfusion [5.14 ± 1.49 vs 4.46 ± 1.73 ml (g*min)^-1; p = 0.036]. A minimal radiation dose applied to the LAD correlated with MBF changes observed 2 months after RT (r = -0.57; p = 0.032). Radiological findings were not correlated with clinical symptoms of heart toxicity.

CONCLUSION

¹⁵O-H₂O PET/CT is safe and effective for the early detection and quantitative analysis of subclinical post-RT changes in heart perfusion in breast cancer patients. The LV segments supplied by the LAD are the main site of MBF changes. A minimum radiation dose deposited in the LAD may be a predictor of radiation-induced heart toxicity. Advances in knowledge: This is the first time that ¹⁵O-H₂O PET/CT has been used to assess MBF after RT and the first granular description of the distribution of blood flow changes after breast cancer RT.

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

Historically, heart dose from left-sided breast radiotherapy has been associated with a risk of cardiac injury. Data suggests that there is not a threshold for the deleterious effects from radiation on the heart. Over the past several years, advances in radiation delivery techniques have reduced cardiac morbidity due to treatment. Deep inspiration breath hold (DIBH) is a technique that takes advantage of a more favorable position of the heart during inspiration to minimize heart doses over a course of radiation therapy. In the accompanying review article, we outline several methods used to deliver treatment with DIBH, quantify the benefits of DIBH treatment, discuss considerations for patient selection, and identify challenges associated with DIBH techniques.

Feasibility study of individualized optimal positioning selection for left-sided whole breast radiotherapy: DIBH or prone

The deep inspiration breath hold (DIBH) and prone (P) position are two common heart-sparing techniques for external-beam radiation treatment of left-sided breast cancer patients. Clinicians select the position that is deemed to be better for tissue sparing based on their experience. This approach, however, is not always optimum and consistent. In response to this, we develop a quantitative tool that predicts the optimal positioning for the sake of organs at risk (OAR) sparing. Sixteen left-sided breast cancer patients were considered in the study, each received CT scans in the supine free breathing, supine DIBH, and prone positions. Treatment plans were generated for all positions. A patient was classified as DIBH or P using two different criteria: if that position yielded (1) lower heart dose, or (2) lower weighted OAR dose. Ten anatomical features were extracted from each patient's data, followed by the principal component analysis. Sequential forward feature selection was implemented to identify features that give the best classification performance. Nine statistical models were then applied to predict the optimal positioning and were evaluated using stratified k-fold cross-validation, predictive accuracy and receiver operating characteristic (AUROC). For heart toxicity-based classification, the support vector machine with radial basis function kernel yielded the highest accuracy (0.88) and AUROC (0.80). For OAR overall toxicities-based classification, the quadratic discriminant analysis achieved the highest accuracy (0.90) and AUROC (0.84). For heart toxicity-based classification, Breast volume and the distance between Heart and Breast were the most frequently selected features. For OAR overall toxicities-based classification, Heart volume, Breast volume and the distance between ipsilateral lung and breast were frequently selected. Given the patient data considered in this study, the proposed statistical model is feasible to provide predictions for DIBH and prone position selection as well as indicate important clinical features that affect the position selection.

Quantification of heart, pericardium, and left ventricular myocardium movements during the cardiac cycle for thoracic tumor radiotherapy

Purpose

The purpose of this study was to quantify variations in the heart, pericardium, and left ventricular myocardium (LVM) caused by cardiac movement using the breath-hold technique.

Patients and methods

In this study, the electrocardiography-gated four-dimensional computed tomography (CT) images of 22 patients were analyzed, which were sorted into 20 phases (0-95%) according to the cardiac cycle. The heart, pericardium, and LVM were contoured on each phase of the CT images. The positions, volume, dice similarity coefficient (DSC) in reference to 0% phase, and morphological parameters (max 3D diameter, roundness, spherical disproportion, sphericity, and surface area) in different phases of the heart, pericardium, and LVM were analyzed, which were presented as mean ± standard deviation.

Results

The mean values of displacements along the X, Y, and Z axes respectively were as follows: 1.2 mm, 0.6 mm, and 0.6 mm for the heart; 0.5 mm, 0.4 mm, and 0.8 mm for the pericardium; and 1.0 mm, 4.1 mm, and 1.9 mm for the LVM. The maximum variations in volume and DSC respectively were 16.49%±3.85% and 10.08%±2.14% for the heart, 12.62%±3.94% and 5.20%±1.54% for the pericardium, and 24.23%±11.35% and 184.33%±128.61% for the LVM. The differences in the morphological parameters between the maximum and minimum DSC phases for the heart and pericardium were not significantly different (p>0.05) but were significantly different for the LVM (p<0.05).

Conclusion

The volumetric and morphological variations of the heart were similar to those of pericardium, and all were significantly smaller than those of the LVM. This inconsistency in the volumetric and morphological variations between the LVM and the heart and pericardium indicates that special protection of the LVM should be considered.

Cardiovascular effects of radiotherapy on the patient with cancer

The incidence of cancer (CA) has increased globally and radiotherapy (RT) is a vital component in its treatment. Cardiovascular injuries induced by RT in the treatment of thoracic and cervical CA have been causing problems in clinical practice for decades, and are among the most serious adverse effects of radiation experienced by the growing number of cancer survivors. This article presentes a review on the Lilacs, Scielo and Pubmed databases of the main cardiovascular injuries, their mechanisms, clinical presentations, treatments and prevention proposals. Injuries caused by RT include diseases of the pericardium, coronary artery disease, valvular disease, myocardial disease with systolic and diastolic dysfunction, conduction disorders, and carotid artery and great vessels disease. Thoracic and cervical irradiation increases cardiovascular morbidity and mortality. Despite the great progress in the improvement of RT techniques, totally excluding prime areas of the cardiovascular system from the irradiation field is not yet possible. Guidelines must be created for monitoring, diagnosis and treatment of patients with CA treated with RT.

Hybrid intensity-modulated radiation therapy (IMRT) simultaneous integrated boost (SIB) technique versus three-dimensional (3D) conformal radiotherapy with SIB for breast radiotherapy: a planning comparison

Aim

This study aims to compare conventional simultaneous integrated boost (SIB) planning technique with a hybrid SIB intensity-modulated radiation therapy (IMRT) technique with varying open tangent to IMRT field dose ratios. Furthermore, we investigated which of the dose ratios proves the most favourable as a class solution across a sample.

Methods

In total, 15 patients with conventional SIB treatment plans were re-planned with hybrid SIB IMRT technique using three differing open field:IMRT dose ratios, that is, 80:20, 70:30 and 60:40. Plans were compared using dosimetric comparison of organs at risk (OARs) and homogeneity and conformity indexes across target structures.

Results

All hybrid plans reduced dose maximums and showed a reduction of high doses to both lungs but increased lower doses, that is, V5, with similar results discovered for the heart. Contralateral breast dose was shown to decrease V5 and V1 measures by hybrid arms, whereas increasing the V2. Left anterior descending artery dose and non-irradiated structures were reduced by all hybrid arms. The homogeneity and conformity increased across all hybrid arms. Qualitative assessment of all plans also favoured hybrid plans.

Findings

Hybrid plans produced superior dose conformity, homogeneity, reduced dose maximums and showed an improvement in most OAR parameters. The 70:30 hybrid technique exhibited greater benefits as a class solution to the sample than conventional plans due to superior dose conformity and homogeneity to target volumes.

Assessing radiation exposure of the left anterior descending artery, heart and lung in patients with left breast cancer: A dosimetric comparison between multicatheter accelerated partial breast irradiation and whole breast external beam radiotherapy

BACKGROUND AND PURPOSE

This study aims to quantify dosimetric reduction to the left anterior descending (LAD) artery, heart and lung when comparing whole breast external beam radiotherapy (WBEBRT) with multicatheter accelerated partial breast irradiation (MCABPI) for early stage left breast cancer.

MATERIALS AND METHODS

Planning CT data sets of 15 patients with left breast cancer receiving multicatheter brachytherapy post breast conserving surgery were used to create two independent treatment plans - WBEBRT prescribed to 50 Gy/25 fractions and MCABPI prescribed to 34 Gy/10 fractions. Dose parameters for (i) LAD artery, (ii) heart, and (iii) ipsilateral lung were calculated and compared between the two treatment modalities.

RESULTS

After adjusting for Equivalent Dose in 2 Gy fractions(EQD2), and comparing MCAPBI with WBEBRT, the largest dose reduction was for the LAD artery whose mean dose differed by a factor of 7.7, followed by the ipsilateral lung and heart with a factor of 4.6 and 2.6 respectively. Compared to WBEBRT, the mean MCAPBI LAD was significantly lower compared to WBEBRT (6.0 Gy vs 45.9 Gy; p<0.01). Mean MCAPBI heart D(0.1cc) (representing the dose received by the most highly exposed 0.1 cc of the risk organ, i.e. the dose peak) was significantly lower (16.3 Gy vs 50.6 Gy; p<0.01). Likewise, the mean heart dose (MHD) was significantly lower (2.3 Gy vs 6.0 Gy; p<0.01). Peak dose and mean lung dose (MLD) for ipsilateral lung was also lower for MCAPBI compared to WBEBRT (Peak dose: 22.2 Gy vs 52.0 Gy; p<0.01; MLD: 2.3 Gy vs 10.7 Gy; p<0.01).

CONCLUSION

Compared to WBEBRT, MCAPBI showed a significant reduction in radiation dose for the LAD, heart and lung. This may translate into better cardiac and pulmonary toxicities for patients undergoing MCAPBI.

Deep inspiration breath-hold technique for left-sided breast cancer: An analysis of predictors for organ-at-risk sparing

To identify anatomic and treatment characteristics that correlate with organ-at-risk (OAR) sparing with deep inspiration breath-hold (DIBH) technique to guide patient selection for this technique. Anatomic and treatment characteristics and radiation doses to OARs were compared between free-breathing and DIBH plans. Linear regression analysis was used to identify factors independently predicting for cardiac sparing. We identified 64 patients: 44 with intact breast and 20 postmastectomy. For changes measured directly on treatment planning scans, DIBH plans decreased heart-chest wall length (6.5 vs 5.0cm, p < 0.001), and increased lung volume (1074.4 vs 1881.3cm(3), p < 0.001), and for changes measured after fields are set, they decreased maximum heart depth (1.1 vs 0.3cm, p < 0.001) and heart volume in field (HVIF) (9.1 vs 0.9cm(3), p < 0.001). DIBH reduced the mean heart dose (3.4 vs 1.8Gy, p < 0.001) and lung V20 (19.6% vs 15.3%, p < 0.001). Regression analysis found that only change in HVIF independently predicted for cardiac sparing. We identified patients in the bottom quartile of the dosimetric benefits seen with DIBH and categorized the cause of this "minimal benefit." Overall, 29% of patients satisfied these criteria for minimal benefit with DIBH and the most common cause was favorable baseline anatomy. Only the reduction in HVIF predicted for reductions in mean heart dose; no specific anatomic surrogate for the dosimetric benefits of DIBH technique could be identified. Most patients have significant dosimetric benefit with DIBH, and this technique should be planned and evaluated for all patients receiving left-sided breast/chest wall radiation.

Image-guided radiotherapy for cardiac sparing in patients with left-sided breast cancer

Patients with left-sided breast cancer are at risk of cardiac toxicity because of cardiac irradiation during radiotherapy with the conventional 3-dimensional conformal radiotherapy technique. In addition, many patients may receive chemotherapy prior to radiation, which may damage the myocardium and may increase the potential for late cardiac complications. New radiotherapy techniques such as intensity-modulated radiotherapy (IMRT) may decrease the risk of cardiac toxicity because of the steep dose gradient limiting the volume of the heart irradiated to a high dose. Image-guided radiotherapy (IGRT) is a new technique of IMRT delivery with daily imaging, which may further reduce excessive cardiac irradiation. Preliminary results of IGRT for cardiac sparing in patients with left-sided breast cancer are promising and need to be investigated in future prospective clinical studies.

Left-sided whole breast irradiation with hybrid-IMRT and helical tomotherapy dosimetric comparison

Purpose. Limited-tomotherapy and hybrid-IMRT treatment techniques were compared for reductions in ipsilateral and contralateral lung, heart, and contralateral breast radiation doses. Methods and Materials. Thirty consecutively treated left-sided early-stage breast cancer patients were scheduled for lTomo and hIMRT. For the hIMRT plan conventional tangential-field and four-field IMRT plans were combined with different weightings in the prescribed dose. For the lTomo plan a geometrically limited arc was designed for the beamlet entrance. A D_p of 50.4 Gy in 28 fractions was used for the PTV. The dose coverage, homogeneity index, conformity index of the target, and the dose volumes of critical structures were compared. Results. Both modalities presented similar target coverage. The homogeneity and conformity were improved for lTomo with P < 0.001 and P = 0.006, respectively. In the lTomo plan a concave dose distribution was generated with significant dose reductions in both high and low dose regions for ipsilateral lung and heart (P < 0.001). Conclusions. lTomo plan can have similar dose coverage and better homogeneity and conformity to the target. By properly designing the directionally and completely blocked structure, lTomo plan was developed successfully in reducing doses to the healthy tissues for early-stage left-sided breast cancer radiotherapy.

Individualized positioning for maximum heart protection during breast irradiation

BACKGROUND

Prone positioning has been found feasible and appropriate for the reduction of radiation exposure of the lungs, but its effects on the heart dose remain controversial. Individual anatomical features were sought for the selection of optimal treatment positioning.

MATERIAL AND METHODS

In 138 left-sided breast cancer cases awaiting postoperative whole-breast radiotherapy, conformal radiotherapy plans were generated in both prone and supine positions.

RESULTS

The radiation doses to the left anterior descending coronary artery (LAD) and heart in the two positions differed individually, and were strongly related to the body mass index (BMI). Image fusion of the CT scans revealed that prone positioning was detrimental if the heart was situated distant from the chest wall in the supine position, but moved to the chest wall in the prone position. For characterization of the geography of the heart and the breast, the median distance between the LAD and the chest wall (dmedian), and the heart area included in the radiation field on a single CT scan at the middle of the heart in the supine position (Aheart) proved most appropriate.

CONCLUSION

A validated statistical model, utilizing the BMI, dmedian and Aheart, permits individualized positioning for maximum heart protection.

Evidence-based risk assessment and recommendations for physical activity clearance: cancer

Physical activity is becoming increasingly acknowledged as an integral component of in the multidisciplinary management of cancer patients. Intensive inquiry in this area is likely to increase further over the next decade; however, cancer-specific, evidence-based risk assessment and recommendations for physical activity are not available. A systematic literature review was performed of all studies conducting an exercise training intervention and (or) any form of objective exercise test among adults diagnosed with cancer. Studies were assessed according to evaluation criteria developed by a panel of experts. A total of 118 studies involving 5529 patients were deemed eligible. Overall, the results suggest that exercise training and maximal and submaximal exercise testing are relatively safe procedures with a total nonlife-threatening adverse event rate of <2%. There was only 1 exercise training-related death. However, the quality of exercise testing methodology and data reporting is less than optimal. Thus, whether the low incidence of events reflects the true safety of exercise training and exercise testing in cancer patients or less than optimal methodology and (or) data reporting remains to be determined. Evidence-based absolute and relative contraindications to physical activity and exercise training and testing are provided as well as probing decision-trees to optimize the adoption and safety of physical activity in persons diagnosed with cancer.

Cardiac complications after radical radiotherapy

Improvements in cancer therapy have led to increasing numbers of cancer survivors, and the long-term complications of these treatments are now becoming apparent. This article presents the current knowledge of adverse cardiovascular effects of radiotherapy to the chest. Medline literature searches relating to the cardiac complications of radiotherapy and subsequent prognosis were conducted. Potential adverse effects of mediastinal irradiation are numerous and can include coronary artery disease, pericarditis, cardiomyopathy, and valvular disease. Damage seems to be related to radiation dose, volume of irradiated heart, age at exposure, technique of chest irradiation, and patient-specific factors. The advent of technology and the newer sophisticated techniques in treatment planning and delivery are expected to decrease the incidence of cardiovascular diseases after radiation of the mediastinal structures. In any case, patients subjected to irradiation of the mediastinal structures require close multidisciplinary clinical monitoring.

Comparison study of the partial-breast irradiation techniques: dosimetric analysis of three-dimensional conformal radiation therapy, electron beam therapy, and helical tomotherapy depending on various tumor locations

The partial-breast irradiation (PBI) technique, an alternative to whole-breast irradiation, is a beam delivery method that uses a limited range of treatment volume. The present study was designed to determine the optimal PBI treatment modalities for 8 different tumor locations. Treatment planning was performed on computed tomography (CT) data sets of 6 patients who had received lumpectomy treatments. Tumor locations were classified into 8 subsections according to breast quadrant and depth. Three-dimensional conformal radiation therapy (3D-CRT), electron beam therapy (ET), and helical tomotherapy (H-TOMO) were utilized to evaluate the dosimetric effect for each tumor location. Conformation number (CN), radical dose homogeneity index (rDHI), and dose delivered to healthy tissue were estimated. The Kruskal-Wallis, Mann-Whitney U, and Bonferroni tests were used for statistical analysis. The ET approach showed good sparing effects and acceptable target coverage for the lower inner quadrant-superficial (LIQ-S) and lower inner quadrant-deep (LIQ-D) locations. The H-TOMO method was the least effective technique as no evaluation index achieved superiority for all tumor locations except CN. The ET method is advisable for treating LIQ-S and LIQ-D tumors, as opposed to 3D-CRT or H-TOMO, because of acceptable target coverage and much lower dose applied to surrounding tissue.

Effect of Bra Use during Radiotherapy for Large-Breasted Women: Acute Toxicity and Treated Heart and Lung Volumes

PURPOSE

Large breast size presents special problems during radiation simulation, planning and patient treatment, including increased skin toxicity, in women undergoing breast-conserving surgery and radiotherapy (BCT). We report our experience using a bra during radiation in large-breasted women and its effect on acute toxicity and heart and lung dosimetry.

MATERIALS AND METHODS

From 2001 to 2006, 246 consecutive large-breasted women (bra size ≥ 38 and/or ≥ D cup) were treated with BCT using either 3D conformal (3D-CRT) or Intensity Modulated Radiation (IMRT). In 58 cases, at the physicians' discretion, a custom-fit bra was used during simulation and treatment. Endpoints were acute radiation dermatitis, and dosimetric comparison of heart and lung volumes in a subgroup of 12 left-sided breast cancer patients planned with and without a bra.

RESULTS

The majority of acute skin toxicities were grade 2 and were experienced by 90% of patients in a bra compared to 70% of patients not in a bra (p=0.003). On multivariate analysis significant predictors of grade 2/3 skin toxicity included 3D-CRT instead of IMRT (OR=3.9, 95% CI:1.8-8.5) and the use of a bra (OR=5.5, 95% CI:1.6-18.8). For left-sided patients, use of a bra was associated with a volume of heart in the treatment fields decreased by 63.4% (p=0.002), a volume of left lung decreased by 18.5% (p=0.25), and chest wall separation decreased by a mean of 1 cm (p=0.03).

CONCLUSIONS

The use of a bra to augment breast shape and position in large-breasted women is an alternative to prone positioning and associated with reduced chest wall separation and reduced heart volume within the treatment field.

Is there a dose-response relationship for heart disease with low-dose radiation therapy?

PURPOSE

To quantify cardiac radiation therapy (RT) exposure using sensitive measures of cardiac dysfunction; and to correlate dysfunction with heart doses, in the setting of adjuvant RT for left-sided breast cancer.

METHODS AND MATERIALS

On a randomized trial, 32 women with node-positive left-sided breast cancer underwent pre-RT stress single photon emission computed tomography (SPECT-CT) myocardial perfusion scans. Patients received RT to the breast/chest wall and regional lymph nodes to doses of 50 to 52.2 Gy. Repeat SPECT-CT scans were performed 1 year after RT. Perfusion defects (PD), summed stress defects scores (SSS), and ejection fractions (EF) were evaluated. Doses to the heart and coronary arteries were quantified.

RESULTS

The mean difference in pre- and post-RT PD was -0.38% ± 3.20% (P=.68), with no clinically significant defects. To assess for subclinical effects, PD were also examined using a 1.5-SD below the normal mean threshold, with a mean difference of 2.53% ± 12.57% (P=.38). The mean differences in SSS and EF before and after RT were 0.78% ± 2.50% (P=.08) and 1.75% ± 7.29% (P=.39), respectively. The average heart Dmean and D95 were 2.82 Gy (range, 1.11-6.06 Gy) and 0.90 Gy (range, 0.13-2.17 Gy), respectively. The average Dmean and D95 to the left anterior descending artery were 7.22 Gy (range, 2.58-18.05 Gy) and 3.22 Gy (range, 1.23-6.86 Gy), respectively. No correlations were found between cardiac doses and changes in PD, SSS, and EF.

CONCLUSIONS

Using sensitive measures of cardiac function, no clinically significant defects were found after RT, with the average heart Dmean <5 Gy. Although a dose response may exist for measures of cardiac dysfunction at higher doses, no correlation was found in the present study for low doses delivered to cardiac structures and perfusion, SSS, or EF.

Accelerated partial breast irradiation using external beam radiotherapy-A feasibility study based on dosimetric analysis

AIM

To investigate the feasibility of using External Beam radiotherapy for accelerated partial breast irradiation by a comparative tumour and normal tissue dose volume analysis with that of high dose rate interstitial brachytherapy.

BACKGROUND

Accelerated Partial Breast Irradiation (APBI) is more clinically appealing because of the reduced treatment course duration and the irradiated area. Brachytherapy application is more dependent on the clinician's expertise when it is practised free hand without image guidance and a template. It happens to be an invasive procedure with the use of local anaesthesia which adds patient discomfort apart from its cost compared to External Beam Radiotherapy. But APBI with brachytherapy is more commonly practised procedure compared to EBRT owing to its previous reults. Hence in this research study, we intend to explore the use of EBRT with the radiobiological corrections for APBI in the place of brachytherapy. It is done as a dosimetric comparison of Brachytherapy treatment plans with that of EBRT plans.

MATERIALS AND METHODS

The computed tomography images of 15 patients undergoing ISBT planning were simulated with conformal photon fields. Various dose volume parameters of each structure were obtained from the DVH generated in the brachytherapy and the simulated external beam planning which can correlate well with the late toxicity. The plan quality indices such as conformity index and homogeneity index for the target volume were computed from the dosimetric factors. The statistical p values for CI, HI and normal tissue dosimetric parameters were calculated and the confidence levels achievable were analysed. The dose prescribed in brachytherapy was 3400cGy in ten fractions. The equivalent prescription dose for the external beam radiotherapy planning was 3000cGy in five fractions applied with radiobiological correction.

RESULTS

All the fifteen patients were with complete lung data and six were with left sided tumours having complete cardiac data. The lung dosimetry data and the cardiac dosimetry data of the patients were studied. Lower percentages of lung and cardiac V 20 and V 5 volumes were obtained with conformal planning. The conformity of radiation dose to the tumour volume was akin to the interstitial brachytherapy planning. Moreover the external beam planning resulted in more homogenous dose distribution. For the sampled population, the statistical analysis showed a confidence level of 95% for using EBRT as an alternate to multi catheter ISBT.

CONCLUSION

The EBRT planning for Accelerated Partial Breast Irradiation was found to be technically feasible in the institution where the interstitial brachytherapy happens to be the only available technique as evident from the dose volume parameters and the statistical analysis.

Quality indicators for breast cancer: revisiting historical evidence in the context of technology changes

Radiation therapy for breast cancer has considerably changed over the years, from simple simulator-based 2-dimensional techniques to sophisticated image-guided individualized treatments, with maximally protected normal structures. This has led to a substantial improvement in the outcome of breast cancer patients in terms of disease control, survival, and quality of life. This progress is based on clinical research and paralleled by progress in delivering sophisticated radiation treatment. Clinical trials resulted in identifying patients groups who will benefit from radiation treatment. They also stimulated the development of quality assurance tools and guidelines, which are now applied in daily clinical practice. The new technical opportunities to optimize dose distributions in patients require dedicated quality assurance measures because they may be more sensitive to variations throughout the treatment. Still, a large source of variation and uncertainty in radiation therapy remains in the definition of target volumes, which is clinically significant in terms of dosimetric target coverage as well as exposure of healthy tissues. This striving for continuous improvement of patient selection and treatment will lead to further improvement of local control while at the same time improving functional and cosmetic outcome and avoiding severe late complications, including cardiac toxicity.

Boosting the tumor bed from deep-seated tumors in early-stage breast cancer: a planning study between electron, photon, and proton beams

PURPOSE

To assess the potential dosimetric advantages and drawbacks of photon beams (modulated or not), electron beams (EB), and protons as a boost for the tumor bed in deep-seated early-stage breast cancer.

MATERIAL AND METHODS

Planning CTs of 14 women with deep-seated tumors (i.e., > or =4 cm depth) were selected. The clinical target volume (CTV) was defined as the area of architectural distortion surrounded by surgical clips. The planning treatment volume (PTV) was the CTV plus 1cm margin. A dose of 16 Gy in 2 Gy fractions was prescribed. Organs at risk (OARs) were heart, lungs, breasts, and a 5-mm thick skin segment on the breast surface. Dose-volume metrics were defined to quantify the quality of concurrent treatment plans assessing target coverage and sparing of OAR. The following treatment techniques were assessed: photon beams with either static 3D-conformal, dynamic arc (DCA), static gantry intensity-modulated beams (IMRT), or RapidArc (RA); a single conformal EB; and intensity-modulated proton beams (IMPT). The goal for this planning effort was to cover 100% of the CTV with 95% of the prescribed dose and to minimize the volume inside the CTV receiving >107% of the dose.

RESULTS

All techniques but DCA and EB achieved the planning objective for the CTV with an inhomogeneity ranging from 2% to 11%. RA showed the best conformity, EB the worst. Contra-lateral breast and lung were spared by all techniques with mean doses <0.5 Gy (zero for protons). The ipsi-lateral lung received a mean dose <10% of that prescribed with photon beams and <2% with IMPT, increasing to 17% with EB. The heart, in left-sided breast tumors, received also the highest dose with EB. The skin was best protected with RA with a mean dose of 5.4 Gy and V(15Gy)=2.4%.

CONCLUSIONS

Boosting the tumor bed in early-stage breast cancer with optimized photon or proton beams may be preferred to EB especially for deep-seated targets. The marked OAR (i.e., ipsi-lateral breast, lung, heart, and skin surface) dose-sparing effect may allow for a potential long-term toxicity risk reduction and better cosmesis. DCA or RA may also be considered alternative treatment options for patients eligible for accelerated partial breast irradiation trials.

Tomotherapy and multifield intensity-modulated radiotherapy planning reduce cardiac doses in left-sided breast cancer patients with unfavorable cardiac anatomy

PURPOSE

For patients with left-sided breast cancers, radiation treatment to the intact breast results in high doses to significant volumes of the heart, increasing the risk of cardiac morbidity, particularly in women with unfavorable cardiac anatomy. We compare helical tomotherapy (TOMO) and inverse planned intensity modulated radiation therapy (IMRT) with three-dimensional conformal radiotherapy using opposed tangents (3D-CRT) for reductions in cardiac volumes receiving high doses.

METHODS AND MATERIALS

Fifteen patients with left-sided breast cancers and unfavorable cardiac anatomy, determined by a maximum heart depth (MHD) of >or=1.0 cm within the tangent fields, were planned for TOMO and IMRT with five to seven beam angles, in addition to 3D-CRT. The volumes of heart and left ventricle receiving >or=35 Gy (V35) were compared for the plans, as were the mean doses to the contralateral breast and the volume receiving >or=20 Gy (V20) for the ipsilateral lung.

RESULTS

The mean MHD was 1.7 cm, and a significant correlation was observed between MHD and both heart and left ventricle V35. The V35s for IMRT (0.7%) and TOMO (0.5%) were significantly lower than for 3D-CRT (3.6%). The V20 for IMRT (22%) was significantly higher than for 3D-CRT (15%) or TOMO (18%), but the contralateral breast mean dose for TOMO (2.48 Gy) was significantly higher than for 3D-CRT (0.93 Gy) or IMRT (1.38 Gy).

CONCLUSIONS

Both TOMO and IMRT can significantly reduce cardiac doses, with modest increases in dose to other tissues in left-sided breast cancer patients with unfavorable cardiac anatomy.

Postoperative proton radiotherapy for localized and locoregional breast cancer: potential for clinically relevant improvements?

PURPOSE

To study the potential reduction of dose to organs at risk (OARs) with intensity-modulated proton radiotherapy (IMPT) compared with intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) photon radiotherapy for left-sided breast cancer patients.

METHODS AND MATERIALS

Comparative treatment-planning was performed using planning computed tomography scans of 20 left-sided breast cancer patients. For each patient, three increasingly complex locoregional volumes (planning target volumes [PTVs]) were defined: whole breast (WB) or chest wall (CW) = (PTV1), WB/CW plus medial-supraclavicular (MSC), lateral-supraclavicular (LSC), and level III axillary (AxIII) nodes = (PTV2) and WB/CW+MSC+LSC+AxIII plus internal mammary chain = (PTV3). For each patient, 3D-CRT, IMRT, and IMPT plans were optimized for PTV coverage. Dose to OARs was compared while maintaining target coverage.

RESULTS

All the techniques met the required PTV coverage except the 3D-CRT plans for PTV3-scenario. All 3D-CRT plans for PTV3 exceeded left-lung V20. IMPT vs. 3D-CRT: significant dose reductions were observed for all OARs using IMPT for all PTVs. IMPT vs. IMRT: For PTV2 and PTV3, low (V5) left lung and cardiac doses were reduced by a factor >2.5, and cardiac doses (V22.5) were by a factor of >20 lower with IMPT compared with IMRT.

CONCLUSIONS

When complex-target irradiation is needed, 3D-CRT often compromises the target coverage and increases the dose to OARs; IMRT can provide better results but will increase the integral dose. The benefit of IMPT is based on improved target coverage and reduction of low doses to OARs, potentially reducing the risk of late-toxicity. These results indicate a potential role of proton-radiotherapy for extended locoregional irradiation in left breast cancer.

[Is cardiotoxicity still an issue after breast-conserving surgery and could it be reduced by multifield IMRT?]

BACKGROUND

Postoperative radiotherapy after breast cancer surgery effectively reduces local relapses. A survival benefit after breast conservation, however, has only been proven recently which was in part due to excessive cardiac mortality of patients who had been treated with radiotherapy in the past.

MATERIAL AND METHODS

The literature on postoperative radiotherapy for breast cancer was reviewed with regard to cardiac toxicity as the basis for hypothesis generation.

RESULTS

From numerous publications on cardiac toxicity of breast cancer radiotherapy, the following pattern emerges: in series where a high radiation dose was applied to a significant percentage of the heart (postmastectomy and postlumpectomy series) cardiac toxicity/mortality was increased versus a nonexposed cohort or for left over right disease. If, however, a relevant exposure of cardiac muscle could be more or less excluded based on the technique used (mainly more recent postlumpectomy radiotherapy), no cardiac toxicity was observed. Series for which individual dose exposure varied or could not be clarified also came to varying conclusions. Also due to retrospectively unclear dose distributions, an exact quantification of tolerance doses/effects of different geographic dose distribution patterns could not be performed to date. A particularly difficult question to answer is the threshold volume for clinically relevant cardiotoxicity with tangential radiotherapy at prescription doses. As a consequence, this precludes an estimate in which situations multifield intensity-modulated radiotherapy (IMRT) with its characteristic dose distribution pattern of a larger volume exposed to intermediate doses and higher mean/median heart doses (as shown in Figure 1) might be preferable.

CONCLUSION

This review updates the database on cardiac toxicity of breast cancer radiotherapy with special emphasis regarding the issues related to the clinical use of IMRT. Multifield IMRT may reduce the cardiac risk for a small subset of patients at excessive risk with conventional tangential radiotherapy due to unfavorable thoracic geometry, for whom partial-breast radiotherapy is not an option. Due to further concern about the effects of intermediate doses to larger heart volumes, potentially increased contralateral cancer risk and the long latency of clinically apparent toxicity, the introduction of breast IMRT should be closely followed. Accompanying functional studies may have the potential to detect cardiac toxicity at an earlier time.

Dose volume histogram analysis of normal structures associated with accelerated partial breast irradiation delivered by high dose rate brachytherapy and comparison with whole breast external beam radiotherapy fields

PURPOSE

To assess the radiation dose delivered to the heart and ipsilateral lung during accelerated partial breast brachytherapy using a MammoSite applicator and compare to those produced by whole breast external beam radiotherapy (WBRT).

MATERIALS AND METHODS

Dosimetric analysis was conducted on patients receiving MammoSite breast brachytherapy following conservative surgery for invasive ductal carcinoma. Cardiac dose was evaluated for patients with left breast tumors with a CT scan encompassing the entire heart. Lung dose was evaluated for patients in whom the entire lung was scanned. The prescription dose of 3400 cGy was 1 cm from the balloon surface. MammoSite dosimetry was compared to simulated WBRT fields with and without radiobiological correction for the effects of dose and fractionation. Dose parameters such as the volume of the structure receiving 10 Gy or more (V10) and the dose received by 20 cc of the structure (D20), were calculated as well as the maximum and mean doses received.

RESULTS

Fifteen patients were studied, five had complete lung data and six had left-sided tumors with complete cardiac data. Ipsilateral lung volumes ranged from 925-1380 cc. Cardiac volumes ranged from 337-551 cc. MammoSite resulted in a significantly lower percentage lung V30 and lung and cardiac V20 than the WBRT fields, with and without radiobiological correction.

CONCLUSION

This study gives low values for incidental radiation received by the heart and ipsilateral lung using the MammoSite applicator. The volume of heart and lung irradiated to clinically significant levels was significantly lower with the MammoSite applicator than using simulated WBRT fields of the same CT data sets.

Cardiac mortality and morbidity after breast cancer treatment

BACKGROUND

Breast conservation treatment for early-stage breast cancer has been demonstrated to be equivalent to mastectomy in a large number of randomized trials. A number of earlier studies of surgery with or without radiation did not show an improvement in overall survival despite large reductions in local recurrence rates. Numerous randomized trials have demonstrated that postmastectomy radiation to the chest wall and regional nodes in high-risk early-stage patients provides improvements in local-regional control and overall survival.

METHODS

This article reviews the medical literature pertaining to long-term cardiac toxicity in early-stage breast cancer patients treated with either breast conservation or postmastectomy radiation.

RESULTS

A decrease in breast cancer deaths associated with postoperative irradiation was offset by an increase in cardiovascular deaths in early studies. Cardiac toxicity of breast irradiation is a late event, manifesting clinically 10 or more years after breast cancer treatment. The excess deaths were directly related to radiation techniques that exposed excessive volumes of the heart, leading to the development of new techniques designed to shield the heart and reduce the risk of cardiac toxicity.

CONCLUSIONS

This review examines the original and contemporary studies of radiation for postmastectomy and breast conservation treatment for early-stage breast cancer, discusses the long-term cardiac mortality and morbidity data from these studies, and reviews the known risk factors associated with cardiac toxicity after irradiation for breast cancer.

Coronary artery disease after radiation therapy for Hodgkin's lymphoma: coronary CT angiography findings and calcium scores in nine asymptomatic patients

OBJECTIVE

Long-term survivors of Hodgkin's lymphoma treated with radiation therapy have an increased incidence of coronary artery disease. The purpose of this study is to describe the coronary CT angiography findings and calcium scores of asymptomatic patients who had mediastinal irradiation for Hodgkin's lymphoma and to evaluate the impact of coronary CT angiography on patient management.

MATERIALS AND METHODS

We evaluated nine consecutive patients, age range 35-60 years, who had been treated for Hodgkin's lymphoma by radiation therapy between the ages of 11 and 27 years. The total mediastinal dose ranged from 34 to 45 Gy. All patients were evaluated with 64-MDCT with calcium scoring followed by CT angiography of the coronary arteries. Imaging findings and clinical follow-up were analyzed.

RESULTS

Eight of nine patients had coronary artery disease. CT showed long segments of diffuse disease; areas of stenosis from soft plaque; and calcification in the proximal right coronary, left anterior descending, and left circumflex arteries. Calcium scores were significantly higher than in other patients of this age group. Additional tests, including selective coronary angiography, were necessary in patients with diffuse disease with calcifications. CT evaluation led to bypass surgery and angioplasty in two patients.

CONCLUSION

Coronary CT angiography and calcium scores are useful tools for evaluation of irradiation-related coronary artery disease. Complementary tests might be necessary in selected patients. Prospective larger studies are needed to better define the role of coronary CT angiography and calcium scores and to establish an algorithm for evaluation and treatment of these patients.