Cardiac doses in post-operative breast irradiation

Cardiac computed tomography in cardio-oncology: an update on recent clinical applications

Chemotherapy and radiotherapy have drastically improved cancer survival, but they can result in significant short- and long-term cardiovascular complications, most commonly heart failure from chemotherapy, whilst radiotherapy increases the risk of premature coronary artery disease (CAD), valve, and pericardial diseases. Cardiac computed tomography (CT) with calcium scoring has a role in screening asymptomatic patients for premature CAD, cardiac CT angiography (CTCA) allows the identification of significant CAD, also in the acute settings where concerns exist towards invasive angiography. CTCA integrates the diagnostic work-up and guides surgical/percutaneous management of valvular heart diseases and allows the assessment of pericardial conditions, including detection of effusion and pericardial calcification. It is a widely available and fast imaging modality that allows a one-step evaluation of CAD, myocardial, valvular, and pericardial disease. This review aims to provide an update on its current use and accompanying evidence-base for cardiac CT in the management of cardio-oncology patients.

Model-based cardiac dose estimation in radiation treatment of left breast cancer

OBJECTIVE:

To develop a mathematical model for cardiac dose estimation for patients who have been treated for left-sided breast cancer without CT data.

METHODS:

After obtaining institutional review board approvals, 147 patients with left-sided breast cancer were selected that were treated supine with opposed tangents. The heart blocks from the tangential fields were removed and dose calculations were performed with 6 MV beams using an advanced algorithm. This study was performed with CT data with DRR to represent a radiographic simulator image of yesteryear treatments. The beam's eye-view images showing delineated breast, lung and heart were created to represent views on radiograph. The maximum heart distance (MHD) was recorded and irradiated heart area (AREA) was computed by combination of triangles and rectangles. Based on accurate 3D dose calculation, mean dose (D_mean) and V₁₀ to V₅₀ of heart were analyzed with respect to MHD and AREA for dosimetric parameters using linear and quadratic fit.

RESULTS:

The treatment parameters calculated by MHD and segments using 2D radiographs were within 2% of the actual dosimetric parameters computed from the 3D planning system. The MHD and AREA vs D_mean, V₁₀, V₂₀, V₃₀ and V₅₀ showed very good correlation with linear model (R² > 0.91); however the correlation was significantly better with quadratic model (R² > 0.92). The analysis of the dosimetric error with our linear and quadratic model is remarkable within <3% error for most cases.

CONCLUSION:

The proposed mathematical model for the cardiac dose estimation is accurate within ±3% using a radiograph without CT data. This provides avenues for patient pooling in future studies related to radiation dose and cardiac toxicity. These results will help in estimating cardiac dose analysis accurately from previous studies as well as in centers still using 2D planning.

ADVANCES IN KNOWLEDGE:

The evidence of cardiac risk following radiotherapy continues to be one of the important considerations for the management of left-sided breast cancer patients. One of the problem in the estimation of dose-risk effects is the reconstruction of heart dose for pre-CT treatments. In this study, a simple mathematical model is presented that could estimate cardiac dose within ±3% in left breast cancer treatment from 2D radiograph where CT data do not exist.

Revision of orthovoltage chest wall treatment using Monte Carlo simulations

PURPOSE

Given the high local control rates observed in breast cancer patients undergoing chest wall irradiation by kilovoltage x-rays, we aimed to revisit this treatment modality by accurate calculation of dose distributions using Monte Carlo simulation.

METHODS AND MATERIAL

The machine components were simulated using the MCNPX code. This model was used to assess the dose distribution of chest wall kilovoltage treatment in different chest wall thicknesses and larger contour or fat patients in standard and mid sternum treatment plans. Assessments were performed at 50 and 100 cm focus surface distance (FSD) and different irradiation angles. In order to evaluate different plans, indices like homogeneity index, conformity index, the average dose of heart, lung, left anterior descending artery (LAD) and percentage target coverage (PTC) were used. Finally, the results were compared with the indices provided by electron therapy which is a more routine treatment of chest wall.

RESULT

These indices in a medium chest wall thickness in standard treatment plan at 50 cm FSD and 15 degrees tube angle was as follows: homogeneity index 2.57, conformity index 7.31, average target dose 27.43 Gy, average dose of heart, lung and LAD, 1.03, 2.08 and 1.60 Gy respectively and PTC 11.19%. Assessments revealed that dose homogeneity in planning target volume (PTV) and conformity between the high dose region and PTV was poor. To improve the treatment indices, the reference point was transferred from the chest wall skin surface to the center of PTV. The indices changed as follows: conformity index 7.31, average target dose 60.19 Gy, the average dose of heart, lung and LAD, 3.57, 6.38 and 5.05 Gy respectively and PTC 55.24%. Coverage index of electron therapy was 89% while it was 22.74% in the old orthovoltage method and also the average dose of the target was about 50 Gy but in the given method it was almost 30 Gy.

CONCLUSION

The results of the treatment study show that the optimized standard and mid sternum treatment for different chest wall thicknesses is with 50 cm FSD and zero (vertical) tube angle, while in large contour patients, it is with 100 cm FSD and zero tube angle. Finally, chest wall kilovoltage and electron therapies were compared, which revealed that electron therapy produces a better dose distribution than kilovoltage therapy.

Late cardiac morbidity of adjuvant radiotherapy for early breast cancer - A population-based study

PURPOSE

The purpose of this study was to assess the long-term cardiac morbidity and mortality after breast irradiation using contemporary irradiation techniques.

METHODS

We used the Catastrophic Illness dataset from the National Health Insurance Research Database to explore the possible association between late cardiotoxicity and women with early breast cancer treated with breast conservation therapy from 2000 to 2010. The Cox proportional-hazards model was used to compare breast cancer patients who received adjuvant radiotherapy versus without adjuvant radiotherapy for the end points with the following primary diagnoses (International Classification of Diseases, 9th Revision codes): ischemic heart disease (410-414, 36.0, 36.1), valvular heart disease (394-397, 424, 35), congestive heart failure (428, 402.01, 402.11, 402.91), and conduction abnormalities (426, 37.7-37.8, 37.94-37.99).

RESULTS

Three hundred and thirty patients received adjuvant radiotherapy and 4802 patients did not receive radiotherapy. Median follow-up was 3.5 years. There was no difference in overall morbidity and mortality from any cardiac cause (p=0.13) in breast cancer patients who received adjuvant radiotherapy versus without radiotherapy by using modern radiotherapy techniques.

CONCLUSION

There were no significant differences in cardiac morbidity and mortality after radiotherapy for breast cancer with a 9-year follow-up period in our population.

Coronary Calcium Scanning in Patients after Adjuvant Radiation for Early Breast Cancer and Ductal Carcinoma In situ

Background and Objective: Radiation therapy (RT) is part of standard adjuvant treatment for breast cancer. Earlier studies demonstrated increased cardiac morbidity and mortality from this. Coronary Calcium scanning utilizing Multidetector Computed Tomography (MDCT) can detect early atherosclerosis in coronary arteries by identifying the amount of calcifications. In our study we employed these tools to detect occult atherosclerosis at least 5 years following breast RT.

Methods: We evaluated 20 asymptomatic patients, <60 years old, treated with RT at least 5 years prior to enrollment. Nine received RT to the left and 11 to the right chest wall. The median interval between RT and calcium scan was 8 years. All patients were treated with external beam RT using tangential technique. All patients underwent MDCT to compute volumetric and Agatston calcium scores of the coronary arteries and the aorta.

Results: Eleven patients had RT to the right chest wall, and eight had a calcium score of 0, while two had minimally elevated scores and one patient had a significantly elevated score. Meanwhile nine patients had RT to the left chest wall, and seven had a calcium score of 0. None had significantly elevated scores. In the aorta, 11 of 20 patients had a score of 0, while 8 of 20 had minimally elevated scores.

Conclusion: In contrast to studies demonstrating increased cardiovascular morbidity, our pilot study did not detect significant occult atherosclerosis using MDCT of the coronaries and aorta of patients assessed five or more years following radiation for treatment of breast cancer.

A comparative dosimetric study for treating left-sided breast cancer for small breast size using five different radiotherapy techniques: conventional tangential field, filed-in-filed, tangential-IMRT, multi-beam IMRT and VMAT

BACKGROUND AND PURPOSES

To compare the dosimetry for the left-sided breast cancer treatment using five different radiotherapy techniques.

MATERIALS AND METHODS

Twenty patients with left sided breast cancer were treated with conservative surgery followed by radiotherapy. They were planned using five different radiotherapy techniques, including: 1) conventional tangential wedge-based fields (TW); 2) field-in-field (FIF) technique; 3) tangential inverse planning intensity-modulated radiation therapy (T-IMRT); 4) multi-field IMRT (M-IMRT); and 5) volumetric modulated arc therapy (VMAT). The CTV, PTV and OARs including the heart, the regions of coronary artery (CA), the contralateral breast, the left and right lung were delineated. The PTV dose was prescribed 50Gy and V47.5≥95%. Same dose constraint was used for all five plans. The planned volumetric dose of PTV and PRV-OARs were compared and analyzed.

RESULTS

Except VMAT (Average V47.5 was 94.72%±1.2%), all the other four plans were able to meet the V95% (V47.5) requirement. T-IMRT plan improved the PTV dose homogeneity index (HI) by 0.02 and 0.03 when compared to TW plan and VMAT plan, and decreased the V5, V10 and V20 of all PRV-OARs. However, the high dose volume (≥ 30Gy) of the PRV-OARs in T-IMRT plan had no statistically significant difference compared with the other two inverse plans. In all five plans, the dose volume of coronary artery area showed a strong correlation to the dose volume of the heart (the correlation coefficients were 0.993, 0.996, 1.000, 0.995 and 0.986 respectively).

CONCLUSION

Compared to other techniques, the T-IMRT technology reduced radiation dose exposure to normal tissues and maintained reasonable target homogeneity, VMAT is not recommended for left-sided breast cancer treatment. In five techniques, the dose-volume histogram (DVH) of the heart can be used to predict the dose-volume histogram (DVH) of the coronary artery.

Dose Distribution in the Heart and Cardiac Chambers Following 4-field Radiation Therapy of Breast Cancer: a Retrospective Study

Purpose:

To evaluate cardiac doses in breast cancer patients with stage II/III treated with 4-field radiotherapy based on computed tomography (CT) dose planning.

Methods and Materials:

Based on archived CT images, whole heart and cardiac chamber radiation doses were analyzed in 216 (111 left-sided and 105 right-sided) mastectomized or lumpectomized breast cancer patients treated at a single institution, the Norwegian Radium Hospital, between 2000–2002. Individual dose volume histograms for the whole heart and for the four cardiac chambers were obtained, and mean, median and maximum doses to these structures were calculated. The dose (Gy) delivered to the 5% of the volume of each cardiac structure (D_5%), and the volume percentage of each structure receiving ≥ 25 Gy (V_25Gy) were reported. Normal tissue complication probability (NTCP) calculations were used to estimate the risk for ischemic heart disease (IHD).

Results:

Cohort-based medians of the whole heart mean dose (D_mean) for left- and right-sided tumors were 3.2 Gy and 1.3 Gy, respectively, with similar ventricular but lower atrial values. The atrial doses did not differ according to laterality of the breast tumor. In 13 patients with left-sided cancer, 5% of the heart volume was exposed to >25 Gy. The NTCP estimates were generelly low, with a maximum of 2.8%.

Conclusions:

During adjuvant CT-based locoregional radiotherapy of women with breast cancer, the cardiac radiation doses are, at the group level, below recommended threshold values (D_5% < 25 Gy), though individual patients with left-sided disease may exceed these limits.

Aortic dose constraints when reirradiating thoracic tumors

BACKGROUND AND PURPOSE

Improved radiation delivery and planning has allowed, in some instances, for the retreatment of thoracic tumors. We investigated the dose limits of the aorta wherein grade 5 aortic toxicity was observed after reirradiation of lung tumors.

MATERIAL AND METHODS

In a retrospective analysis, 35 patients were identified, between 1993 and 2008, who received two rounds of external beam irradiation that included the aorta in the radiation fields of both the initial and retreatment plans. We determined the maximum cumulative dose to 1 cm(3) of the aorta (the composite dose) for each patient, normalized these doses to 1.8 Gy/fraction, and corrected them for long-term tissue recovery between treatments (NIDR).

RESULTS

The median time interval between treatments was 30 months (range, 1-185 months). The median follow-up of patients alive at analysis was 42 months (range, 14-70 months). Two of the 35 patients (6%) were identified as having grade 5 aortic toxicities. There was a 25% rate of grade 5 aortic toxicity for patients receiving composite doses ≥120.0 Gy (vs. 0% for patients receiving <120.0 Gy) (P=0.047).

CONCLUSIONS

Grade 5 aortic toxicities were observed with composite doses ≥120.0 Gy (NIDR ≥90.0 Gy) to 1cm(3) of the aorta.

Cardiac motion during deep-inspiration breath-hold: implications for breast cancer radiotherapy

PURPOSE

Many patients with left-sided breast cancer receive adjuvant radiotherapy during deep-inspiration breath hold (DIBH) to minimize radiation exposure to the heart. We measured the displacement of the left anterior descending artery (LAD) and heart owing to cardiac motion during DIBH, relative to the standard tangential fields for left breast cancer radiotherapy.

METHODS AND MATERIALS

A total of 20 patients who had undergone computed tomography-based coronary angiography with retrospective electrocardiographic gating were randomly selected for the present study. The patients underwent scanning during DIBH to control the influence of respiration on cardiac motion. Standard medial and lateral tangential fields were placed, and the LADs were contoured on the systolic- and diastolic-phase computed tomography data sets by the clinicians. Displacement of the LAD during cardiac contractions was calculated in three directions: toward the posterior edge of the treatment fields, left-right, and anteroposterior. Displacement of the entire heart was measured on the maximal and minimal intensity projection computed tomography images.

RESULTS

The mean displacement of the LAD from cardiac contraction without the influence of respiration for 20 patients was 2.3 mm (range, 0.7-3.8) toward the posterior edge of the treatment fields, 2.6 mm (range, 1.0-6.8) in the left-right direction, and 2.3 mm (range, 0.6-6.5) in the anteroposterior direction. At least 30% of the LAD volume was displaced >5 mm in any direction in 2 patients (10%), and <10% of the LAD volume was displaced >5 mm in 10 patients (50%). The extent of displacement of the heart periphery during cardiac motion was negligible near the treatment fields.

CONCLUSIONS

Displacement of the heart periphery near the treatment fields was negligible during DIBH; however, displacement of the LAD from cardiac contraction varied substantially between and within patients. We recommend maintaining ≥ 5 mm of distance between the LAD and the field edge for patients undergoing breast cancer radiotherapy during DIBH.

Cardiac dose estimates from Danish and Swedish breast cancer radiotherapy during 1977-2001

Background and purpose

To estimate target and cardiac doses from breast cancer radiotherapy in Denmark and in the Stockholm and Umeå areas of Sweden during 1977–2001.

Methods

Representative samples of irradiated women were identified from the databases of the Danish Breast Cancer Cooperative Group and the Swedish Nationwide Cancer Registry. Virtual simulation, computed tomography planning and manual planning were used to reconstruct radiotherapy regimens on a typical woman. Estimates of target dose and various measures of cardiac dose were derived from individual radiotherapy charts.

Results

Doses were estimated in 681 Danish and 130 Swedish women. Mean heart dose for individual women varied from 1.6 to 14.9 Gray in Denmark and from 1.2 to 22.1 Gray in Sweden. In Denmark, mean target doses averaged across women increased from 40.6 to 53.8 Gray during 1977–2001 but, despite this, mean heart dose averaged across women remained around 6 Gy for left-sided and 2–3 Gray for right-sided radiotherapy. In Sweden mean target dose averaged across women increased from 38.7 to 46.6 Gray during 1977–2001, while mean heart dose averaged across women decreased from 12.0 to 7.3 Gray for left-sided and from 3.6 to 3.2 Gray for right-sided radiotherapy. Temporal trends for mean biologically effective dose [BED] to the heart, mean dose to the left anterior descending coronary artery, the right coronary artery and the circumflex coronary artery were broadly similar.

Conclusions

Cardiac doses in Denmark were low relative to those in Sweden. In both countries, target dose increased during 1977–2001. Despite this, cardiac doses remained constant in Denmark and decreased in Sweden.

Successful radiation treatment of anaplastic thyroid carcinoma metastatic to the right cardiac atrium and ventricle in a pacemaker-dependent patient

Anaplastic thyroid carcinoma (ATC) is a rare, aggressive malignancy, which is known to metastasize to the heart. We report a case of a patient with ATC with metastatic involvement of the pacemaker leads within the right atrium and right ventricle. The patient survived external beam radiation treatment to his heart, with a radiographic response to treatment. Cardiac metastases are usually reported on autopsy; to our knowledge, this is the first report of the successful treatment of cardiac metastases encasing the leads of a pacemaker, and of cardiac metastases from ATCs, with a review of the pertinent literature.

An ultrasonographic evaluation of skin thickness in breast cancer patients after postmastectomy radiation therapy

BACKGROUND

To determine the usefulness of ultrasonography in the assessment of post radiotherapy skin changes in postmastectomy breast cancer patients.

METHODS

Patients treated for postmastectomy radiotherapy in National University Hospital (NUH) and Tan Tock Seng Hospital (TTSH), Singapore between January 2004- December 2005 was recruited retrospectively. Ultrasound scan was performed on these Asian patients who had been treated to a total dose of 46-50 Gy with 1 cm bolus placed on the skin. The ultrasound scans were performed blinded to the RTOG scores, and the skin thickness of the individually marked points on the irradiated chest wall was compared to the corresponding points on the non-irradiated breast.

RESULTS

The mean total skin thickness inclusive of the epidermis and the dermis of the right irradiated chest wall was 0.1712 mm (± 0.03392 mm) compared with the contra-lateral non-irradiated breast which was 0.1845 mm (± 0.04089 mm; p = 0.007). The left irradiated chest wall had a mean skin thickness of 0.1764 mm (± 0.03184 mm) compared with the right non-irradiated breast which was 0.1835 mm (± 0.02584 mm; p = 0.025). These independent t-tests produced a significant difference of reduced skin thickness on the right irradiated chest wall, p = 0.007 (p < 0.05) and left irradiated chest wall p = 0.025 (p < 0.025) in comparison to the non-irradiated skin thickness investigating chronic skin reactions. Patients with grade 2 acute skin toxicity presented with thinner skin as compared to patients with grade 1 (p = 0.006).

CONCLUSIONS

This study has shown that there is a statistically significant difference between the skin thicknesses of the irradiated chest wall and the contra-lateral non-irradiated breast and a predisposition to chronic reactions was found in patients with acute RTOG scoring of grade1 and grade 2.

Doses to internal organs for various breast radiation techniques--implications on the risk of secondary cancers and cardiomyopathy

Background

Breast cancers are more frequently diagnosed at an early stage and currently have improved long term outcomes. Late normal tissue complications induced by adjuvant radiotherapy like secondary cancers or cardiomyopathy must now be avoided at all cost. Several new breast radiotherapy techniques have been developed and this work aims at comparing the scatter doses of internal organs for those techniques.

Methods

A CT-scan of a typical early stage left breast cancer patient was used to describe a realistic anthropomorphic phantom in the MCNP Monte Carlo code. Dose tally detectors were placed in breasts, the heart, the ipsilateral lung, and the spleen. Five irradiation techniques were simulated: whole breast radiotherapy 50 Gy in 25 fractions using physical wedge or breast IMRT, 3D-CRT partial breast radiotherapy 38.5 Gy in 10 fractions, HDR brachytherapy delivering 34 Gy in 10 treatments, or Permanent Breast ¹⁰³Pd Seed Implant delivering 90 Gy.

Results

For external beam radiotherapy the wedge compensation technique yielded the largest doses to internal organs like the spleen or the heart, respectively 2,300 mSv and 2.7 Gy. Smaller scatter dose are induced using breast IMRT, respectively 810 mSv and 1.1 Gy, or 3D-CRT partial breast irradiation, respectively 130 mSv and 0.7 Gy. Dose to the lung is also smaller for IMRT and 3D-CRT compared to the wedge technique. For multicatheter HDR brachytherapy a large dose is delivered to the heart, 3.6 Gy, the spleen receives 1,171 mSv and the lung receives 2,471 mSv. These values are 44% higher in case of a balloon catheter. In contrast, breast seeds implant is associated with low dose to most internal organs.

Conclusions

The present data support the use of breast IMRT or virtual wedge technique instead of physical wedges for whole breast radiotherapy. Regarding partial breast irradiation techniques, low energy source brachytherapy and external beam 3D-CRT appear safer than ¹⁹²Ir HDR techniques.

Radiation techniques and toxicities for locally advanced breast cancer

Radiation therapy is used in the management of locally advanced breast cancer in the postmastectomy or neoadjuvant chemotherapy and breast-conservation setting to improve local-regional control and survival. Using modern-day technology, the therapeutic ratio has increased and the potential morbidity has decreased. This article reviews the technical aspects of radiation therapy for locally advanced breast cancer with emphasis on 3-dimensional radiotherapy techniques and discusses potential toxicities and how to reduce them.

Evaluation of multiple breathing states using a multiple instance geometry approximation (MIGA) in inverse-planned optimization for locoregional breast treatment

PURPOSE

Although previous work demonstrated superior dose distributions for left-sided breast cancer patients planned for intensity-modulated radiation therapy (IMRT) at deep inspiration breath hold compared with conventional techniques with free-breathing, such techniques are not always feasible to limit the impact of respiration on treatment delivery. This study assessed whether optimization based on multiple instance geometry approximation (MIGA) could derive an IMRT plan that is less sensitive to known respiratory motions.

METHODS AND MATERIALS

CT scans were acquired with an active breathing control device at multiple breath-hold states. Three inverse optimized plans were generated for eight left-sided breast cancer patients: one static IMRT plan optimized at end exhale, two (MIGA) plans based on a MIGA representation of normal breathing, and a MIGA representation of deep breathing, respectively. Breast and nodal targets were prescribed 52.2 Gy, and a simultaneous tumor bed boost was prescribed 60 Gy.

RESULTS

With normal breathing, doses to the targets, heart, and left anterior descending (LAD) artery were equivalent whether optimizing with MIGA or on a static data set. When simulating motion due to deep breathing, optimization with MIGA appears to yield superior tumor-bed coverage, decreased LAD mean dose, and maximum heart and LAD dose compared with optimization on a static representation.

CONCLUSIONS

For left-sided breast-cancer patients, inverse-based optimization accounting for motion due to normal breathing may be similar to optimization on a static data set. However, some patients may benefit from accounting for deep breathing with MIGA with improvements in tumor-bed coverage and dose to critical structures.

Association between tangential beam treatment parameters and cardiac abnormalities after definitive radiation treatment for left-sided breast cancer

PURPOSE

To examine the association between radiation treatment (RT) parameters, cardiac diagnostic test abnormalities, and clinical cardiovascular diagnoses among patients with left-sided breast cancer after breast conservation treatment with tangential beam RT.

METHODS AND MATERIALS

The medical records of 416 patients treated between 1977 and 1995 with RT for primary left-sided breast cancer were reviewed for myocardial perfusion imaging and echocardiograms. Sixty-two patients (62/416, 15%) underwent these cardiac diagnostic tests for cardiovascular symptoms and were selected for further study. Central lung distance and maximum heart width and length in the treatment field were determined for each patient. Medical records were reviewed for cardiovascular diagnoses and evaluation of cardiac risk factors.

RESULTS

At a median of 12 years post-RT the incidence of cardiac diagnostic test abnormalities among symptomatic left-sided irradiated women was significantly higher than the predicted incidence of cardiovascular disease in the patient population, 6/62 (9%) predicted vs. 24/62 (39%) observed, p = 0.001. As compared with patients with normal tests, patients with cardiac diagnostic test abnormalities had a larger median central lung distance (2.6 cm vs. 2.2 cm, p = 0.01). Similarly, patients with vs. without congestive heart failure had a larger median central lung distance (2.8 cm vs. 2.3 cm, p = 0.008).

CONCLUSIONS

Contemporary RT for early breast cancer may be associated with a small, but potentially avoidable, risk of cardiovascular morbidity that is associated with treatment technique.

Cardiovascular effects of breast cancer radiotherapy

Cardiac toxicity has been implicated as the primary reason for excess non-breast cancer mortality in early breast cancer radiotherapy studies. Refinements in radiotherapy techniques have allowed for a considerable reduction of this risk in the majority of breast cancer patients. Recent large population-based studies confirmed an increase of cardiovascular death risk in patients irradiated for cancer of the left breast and in individuals exposed to relatively low (hitherto believed to be of no cardiovascular disease risk) doses of radiation, such as atomic bomb survivors or patients treated for various benign conditions. The issue of potential radiation-related cardiac damage may also be assuming a new significance due to the widespread use of other cardiotoxic agents, such as anthracyclines, paclitaxel and trastuzumab. The aim of this review is to summarize and critically analyze the available evidence on the impact of ionizing radiation on the cardiovascular system, with special attention to recent data demonstrating previously unrecognized adverse effects. This review discusses the pathology of radiation-related cardiovascular disease, its clinical presentation, risk factors and methods of assessment, as well as technical developments minimizing cardiac exposure. Epidemiological data are presented on the incidence of radiation-induced heart disease and cardiovascular mortality in various populations of patients irradiated for breast cancer and in individuals exposed to low radiation doses. Additionally, non-cardiac radiation-related vascular morbidity and mortality in breast cancer patients are addressed.

Short-term displacement and reproducibility of the breast and nodal targets under active breathing control

PURPOSE

The short-term displacement and reproducibility of the breast or chest wall, and the internal mammary (IM), infraclavicular (ICV), and supraclavicular (SCV) nodal regions have been assessed as a function of breath-hold state using an active breathing control (ABC) device for patients receiving loco-regional breast radiation therapy.

METHODS AND MATERIALS

Ten patients underwent computed tomographic scanning using an ABC device at breath-hold states of end-exhale and 20%, 40%, 60%, and 80% of vital capacity (VC). Patients underwent scanning before treatment and at one third and two thirds of the way through treatment. A regional registration was performed for each target using a rigid-body transformation with mutual information as a metric.

RESULTS

Between exhale and 40% of VC, the mean displacement was 0.27/0.34, 0.24/0.31, 0.22/0.19, and 0.13/0.19 cm anterior/superior for the breast or chest wall, and IM, ICV, and SCV nodes, respectively. At 80% of VC, the mean displacement from exhale was 0.84/.88, 0.76/.79, 0.70/0.79, and 0.54/0.56 cm anterior/superior for the breast or chest wall, and IM, ICV, and SCV nodes, respectively. The short-term reproducibility (standard deviation) was <0.3 and <or=0.4 cm for 40% and 80% of VC, respectively. Displacements up to 1.9 cm were observed for individual patients.

CONCLUSIONS

The short-term reproducibility of target position is <or=0.4 cm using ABC for all structures for all breath-hold states. This information can be used to guide treatment planning optimization studies that consider the effect of motion on target and normal tissue doses with and without active breathing control.

Radiation therapy, cardiac risk factors, and cardiac toxicity in early-stage breast cancer patients

PURPOSE

The benefits of adjuvant radiation therapy (RT) for breast cancer may be counterbalanced by the risk of cardiac toxicity. We studied the cardiac effects of RT and the impact of pre-existing cardiac risk factors (CRFs) in a population-based sample of older patients with breast cancer.

METHODS AND MATERIALS

In the Surveillance, Epidemiology and End-Results (SEER)-Medicare database of women > or = 65 years diagnosed with Stages I to III breast cancer from January 1, 1992 to December 31, 2000, we used multivariable logistic regression to model the associations of demographic and clinical variables with postmastectomy and postlumpectomy RT. Using Cox proportional hazards regression, we then modeled the association between treatment and myocardial infarction (MI) and ischemia in the 10 or more years after diagnosis, taking the predictors of treatment into account.

RESULTS

Among 48,353 women with breast cancer; 19,897 (42%) were treated with lumpectomy and 26,534 (55%) with mastectomy; the remainder had unknown surgery type (3%). Receipt of RT was associated with later year of diagnosis, younger age, fewer comorbidities, nonrural residence, and chemotherapy. Postlumpectomy RT was also associated with white ethnicity and no prior history of heart disease (HD). The RT did not increase the risk of MI. Presence of MI was associated with age, African American ethnicity, advanced stage, nonrural residence, more than one comorbid condition, a hormone receptor-negative tumor, CRFs and HD. Among patients who received RT, tumor laterality was not associated with MI outcome. The effect of RT on the heart was not influenced by HD or CRFs.

CONCLUSION

It appears unlikely that RT would increase the risk of MI in elderly women with breast cancer, regardless of type of surgery, tumor laterality, or history of CRFs or HD, for at least 10 years.

A population-based case-cohort study of the risk of myocardial infarction following radiation therapy for breast cancer

OBJECTIVE

To describe the risk of acute myocardial infarction (AMI) after radiation therapy (RT) for breast cancer (BrCa) in an exposed population.

METHODS

We identified and validated cases of AMI (vAMI), by electrocardiographic or enzyme criteria, among all 6680 women who received post-operative RT following lumpectomy or mastectomy, within 12 months following diagnosis of BrCa between 1982 and 1988 in Ontario, Canada. We identified women without vAMI whose death certification was ascribed to AMI (dAMI). We abstracted risk factors and treatment exposures for a random sample of women from the 6680, and for all with vAMI or dAMI. The hazards of vAMI and of dAMI were estimated using multivariate Cox proportional hazards models, corrected for study design.

RESULTS

We validated 121 cases of vAMI and identified 92 cases of dAMI. The risk of vAMI associated with RT to the left breast HR=1.96 (1.09,3.54) among women at age >/= 60 at time of RT, adjusted for history of smoking and prior MI. The adjusted HR dAMI=1.90 (1.08,3.35) for exposure to anterior internal mammary node (IMC) RT. Among women who received anterior left breast boost RT, increasing area of the boost is associated with adjusted HR vAMI=1.02 (1.00,1.03)/cm(2), and adjusted HR dAMI=1.02 (1.01,1.03)/cm(2).

CONCLUSION

The risks of vAMI and dAMI following RT for BrCa are related to anatomic sites of RT (left breast, area of anterior left breast boost field, and anterior IMC field).

The utility of 18F-fluorodeoxyglucose positron emission tomography for early diagnosis of radiation-induced myocardial damage

PURPOSE

We evaluated the clinical significance of focal increased uptake in the basal myocardium on F-fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with esophageal cancer after radiotherapy.

METHODS AND MATERIALS

Between August 2004 and July 2005, a total of 64 patients who had been irradiated for thoracic esophageal cancer underwent FDG-PET at least three months after the completion of chemoradiotherapy. Some patients showed increased FDG uptake in the basal portion of the myocardium. To clarify the clinical significance of these findings, further examinations of hearts were performed. The dose distribution in the myocardium with high FDG uptake was also analyzed retrospectively.

RESULTS

Thirteen (20.3%) of the 64 patients showed high FDG uptake in the basal myocardium corresponding to the irradiated fields compared with FDG uptake in the myocardium outside the irradiated fields. Eight of the 13 patients consented to undergo examinations of the heart. Five of those eight patients showed low 123I-BMIPP uptake and four showed low 201TlCl uptake in the myocardium corresponding with high FDG uptake regions. In two patients, delayed enhancement was found in some parts of the area with high FDG uptake on Gd-DTPA magnetic resonance imaging (MRI), and the delay-enhanced lesion showed hypokinesia on cine-MRI in one patient.

CONCLUSIONS

FDG-PET often shows focal increased uptake in the basal myocardium after radiotherapy for esophageal cancer. This finding indicates the possibility of radiation-induced cardiac damage, and cardiac function and symptoms of such patients should be followed carefully.

Cardiac Risks of Breast-cancer Radiotherapy: A Contemporary View

For some time, there has been compelling evidence both from randomised-controlled trials and from observational studies, that some of the breast-cancer radiotherapy regimens used in the past have led to increased risk of mortality from heart disease. There is also some evidence that the more recent regimens used in the USA are associated with lower risks than previous ones, but it is not clear whether current regimens are free from cardiac risk, especially in the light of recent evidence from the survivors of the bombings of Hiroshima and Nagasaki, in whom a clear relationship was observed between the risk of mortality from heart disease and radiation dose for doses in the range 0-4 Gy. Mortality from radiation-induced heart disease usually occurs at least a decade after irradiation. Symptomatic heart disease might have a much shorter induction period, but little information about it is available at present. Subclinical vascular abnormalities have been observed within months of irradiation, via myocardial perfusion imaging studies, but little is known about the relationship between these and later overt heart disease. At present, few data relate heart dose and other specific characteristics of breast radiotherapy to cardiac outcome. Further information on these topics is needed to enable estimation of the cardiac risk, that is likely to arise from radiotherapy regimens in current use and from those being considered for future use. Such knowledge would facilitate radiotherapy treatment planning and enable a reduction in cardiac risk while maintaining the known benefit in terms of breast cancer mortality.

Effects of radiotherapy and of differences in the extent of surgery for early breast cancer on local recurrence and 15-year survival: an overview of the randomised trials

BACKGROUND

In early breast cancer, variations in local treatment that substantially affect the risk of locoregional recurrence could also affect long-term breast cancer mortality. To examine this relationship, collaborative meta-analyses were undertaken, based on individual patient data, of the relevant randomised trials that began by 1995.

METHODS

Information was available on 42,000 women in 78 randomised treatment comparisons (radiotherapy vs no radiotherapy, 23,500; more vs less surgery, 9300; more surgery vs radiotherapy, 9300). 24 types of local treatment comparison were identified. To help relate the effect on local (ie, locoregional) recurrence to that on breast cancer mortality, these were grouped according to whether or not the 5-year local recurrence risk exceeded 10% (<10%, 17,000 women; >10%, 25,000 women).

FINDINGS

About three-quarters of the eventual local recurrence risk occurred during the first 5 years. In the comparisons that involved little (<10%) difference in 5-year local recurrence risk there was little difference in 15-year breast cancer mortality. Among the 25,000 women in the comparisons that involved substantial (>10%) differences, however, 5-year local recurrence risks were 7% active versus 26% control (absolute reduction 19%), and 15-year breast cancer mortality risks were 44.6% versus 49.5% (absolute reduction 5.0%, SE 0.8, 2p<0.00001). These 25,000 women included 7300 with breast-conserving surgery (BCS) in trials of radiotherapy (generally just to the conserved breast), with 5-year local recurrence risks (mainly in the conserved breast, as most had axillary clearance and node-negative disease) 7% versus 26% (reduction 19%), and 15-year breast cancer mortality risks 30.5% versus 35.9% (reduction 5.4%, SE 1.7, 2p=0.0002; overall mortality reduction 5.3%, SE 1.8, 2p=0.005). They also included 8500 with mastectomy, axillary clearance, and node-positive disease in trials of radiotherapy (generally to the chest wall and regional lymph nodes), with similar absolute gains from radiotherapy; 5-year local recurrence risks (mainly at these sites) 6% versus 23% (reduction 17%), and 15-year breast cancer mortality risks 54.7% versus 60.1% (reduction 5.4%, SE 1.3, 2p=0.0002; overall mortality reduction 4.4%, SE 1.2, 2p=0.0009). Radiotherapy produced similar proportional reductions in local recurrence in all women (irrespective of age or tumour characteristics) and in all major trials of radiotherapy versus not (recent or older; with or without systemic therapy), so large absolute reductions in local recurrence were seen only if the control risk was large. To help assess the life-threatening side-effects of radiotherapy, the trials of radiotherapy versus not were combined with those of radiotherapy versus more surgery. There was, at least with some of the older radiotherapy regimens, a significant excess incidence of contralateral breast cancer (rate ratio 1.18, SE 0.06, 2p=0.002) and a significant excess of non-breast-cancer mortality in irradiated women (rate ratio 1.12, SE 0.04, 2p=0.001). Both were slight during the first 5 years, but continued after year 15. The excess mortality was mainly from heart disease (rate ratio 1.27, SE 0.07, 2p=0.0001) and lung cancer (rate ratio 1.78, SE 0.22, 2p=0.0004).

INTERPRETATION

In these trials, avoidance of a local recurrence in the conserved breast after BCS and avoidance of a local recurrence elsewhere (eg, the chest wall or regional nodes) after mastectomy were of comparable relevance to 15-year breast cancer mortality. Differences in local treatment that substantially affect local recurrence rates would, in the hypothetical absence of any other causes of death, avoid about one breast cancer death over the next 15 years for every four local recurrences avoided, and should reduce 15-year overall mortality.

Long-term follow-up of a randomised trial designed to determine the need for irradiation following conservative surgery for the treatment of invasive breast cancer

Four hundred consecutive patients aged under 70 years diagnosed with a clinical T1 or T2 breast cancer were randomised to receive post-operative radiotherapy (n = 208) or not (n = 192), and monitored to record all local recurrences, distant recurrences and deaths for up to 20 years (median 13.7 years). All patients were treated by wide local excision and adjuvant therapy [estrogen receptor (ER) positive: tamoxifen; ER negative: CMF chemotherapy]. Kaplan-Meier and log-rank test methods were used to estimate and compare survival and recurrence. The 20-year Kaplan-Meier rates for local breast recurrence were 28.6% [95% confidence interval (CI) 19.6% to 37.6%] for radiotherapy and 49.8% (95% CI 40.8% to 58.9%). There was no significant difference between the two groups with regard to disease-free or overall survival. The hazard ratio for death among women who received radiation, as compared with those that did not, was 0.91 (95% CI 0.64-1.28; P = 0.59). Therefore, post-operative radiotherapy produced a clear-cut reduction in locoregional recurrence 0.45 (0.31-0.64; P = 0.0001), but did not influence the incidence of distant metastases or time of death. However, of the 119 patients who had a local recurrence, 51 (42.8%) had a distant recurrence, whereas of the 281 without local recurrence only 59 (21%) ever had a distant recurrence. A Cox's regression analysis with local recurrence as a time-dependent variable showed a risk ratio of 5.28 (P < 0.0001). This strong relationship is dependent on the intensity of post-treatment follow-up and investigation.

Cardiac Morbidity of Adjuvant Radiotherapy for Breast Cancer

Purpose

Adjuvant breast irradiation has been associated with an increase in cardiac mortality, because left-sided breast radiation can produce cardiac damage. The purpose of this study was to determine whether modern adjuvant radiotherapy is associated with increased risk of cardiac morbidity.

Patients and Methods

Data from the Surveillance, Epidemiology, and End Results–Medicare database were used for women who were diagnosed with nonmetastatic breast cancer from 1986 to 1993, had known disease laterality, underwent breast surgery, and received adjuvant radiotherapy. The Cox proportional-hazards model was used to compare patients with left- versus right-sided breast cancer for the end points of hospitalization with the following discharge diagnoses (International Classification of Diseases, 9th Revision codes): ischemic heart disease (410-414, 36.0, and 36.1), valvular heart disease (394-397, 424, 35), congestive heart failure (428, 402.01, 402.11, 402.91, and 425), and conduction abnormalities (426, 427, 37.7-37.8, and 37.94-37.99).

Results

Eight thousand three hundred sixty-three patients had left-sided breast cancer, and 7,907 had right-sided breast cancer. Mean follow-up was 9.5 years (range, 0 to 15 years). There were no significant differences in patients with left- versus right-sided cancers for hospitalization for ischemic heart disease (9.9% v 9.7%), valvular heart disease (2.9% v 2.8%), conduction abnormalities (9.7% v 9.6%), or heart failure (9.7% v 9.7%). The adjusted hazard ratio for left- versus right-sided breast cancer was 1.05 (95% CI, 0.94 to 1.16) for ischemic heart disease, 1.07 (95% CI, 0.89 to 1.30) for valvular heart disease, 1.07 (95% CI, 0.96 to 1.19) for conduction abnormalities, and 1.05 (95% CI, 0.95 to 1.17) for heart failure.

Conclusion

With up to 15 years of follow-up there were no significant differences in cardiac morbidity after radiation for left- versus right-sided breast cancer.

Long-term mortality from heart disease and lung cancer after radiotherapy for early breast cancer: prospective cohort study of about 300,000 women in US SEER cancer registries

BACKGROUND

Radiotherapy for early breast cancer can decrease breast cancer mortality but increase other mortality, mainly from heart disease and lung cancer. The mean cardiac dose from irradiation of a left-sided breast cancer can be two or three times that for a right-sided breast cancer. The mean ipsilateral (ie, on the same side as the breast cancer) lung dose can also be two or three times the mean contralateral lung dose. Particularly during the 1970s, when typical heart and lung exposures were greater than now, the laterality of an irradiated breast cancer could measurably affect cardiac mortality and mortality from cancer of the right or the left lung decades later. This study aimed to assess the hazards in the general US population from routine cancer-registry and death-certificate data.

METHODS

We analysed data for 308 861 US women with early breast cancer of known laterality (left-sided or right-sided) who were registered in the US Surveillance Epidemiology and End Results (SEER) cancer registries during 1973-2001 and followed prospectively for cause-specific mortality until Jan 1, 2002.

FINDINGS

115 165 (37%) received radiotherapy. Among those who did not, tumour laterality was of little relevance to subsequent mortality. For women diagnosed during 1973-82 and irradiated, the cardiac mortality ratio (left versus right tumour laterality) was 1.20 (95% CI 1.04-1.38) less than 10 years afterwards, 1.42 (1.11-1.82) 10-14 years afterwards, and 1.58 (1.29-1.95) after 15 years or more (trend: 2p=0.03). For women diagnosed during 1983-92 and irradiated, the cardiac mortality ratio was 1.04 (0.91-1.18) less than 10 years afterwards and 1.27 (0.99-1.63) 10 or more years afterwards. For women diagnosed during 1993-2001 and irradiated the cardiac mortality ratio was 0.96 (0.82-1.12), with none yet followed for 10 years. Among women irradiated for breast cancer who subsequently developed an ipsilateral or contralateral lung cancer, the lung cancer mortality ratio (ipsilateral versus contralateral) for women diagnosed during 1973-82 and irradiated was 1.17 (0.62-2.19), 2.00 (1.00-4.00), and 2.71 (1.65-4.48), respectively, less than 10 years, 10-14 years, and 15 or more years afterwards (trend: 2p=0.04). For women irradiated after 1982 there is, as yet, little information on lung cancer risks more than 10 years afterwards.

INTERPRETATION

US breast cancer radiotherapy regimens of the 1970s and early 1980s appreciably increased mortality from heart disease and lung cancer 10-20 years afterwards with, as yet, little direct evidence on the hazards after more than 20 years. Since the early 1980s, improvements in radiotherapy planning should have reduced such risks, but the long-term hazards in the general populations of various countries still need to be monitored directly.

Complications of radiotherapy: improving the therapeutic index

For every course of radiotherapy treatment, the potential benefit has to be weighed against the risk of normal tissue damage. Radiation-induced proctitis during and after radical radiotherapy for prostate cancer can be decreased by reducing both the size of the target volume and the margins required around this volume. In the future, target volumes could be reduced by both CT/MRI co-registration and dose painting using MR spectroscopy of choline and citrate in the prostate. Improved immobilisation and image-guided radiotherapy should allow reduced margins without compromising the effectiveness of treatment. Similarly, in breast radiotherapy treatment, lung and cardiac complications can be reduced by better patient positioning and ensuring that doses to the heart and lung are minimised during radiotherapy treatment planning. Cosmesis can be improved by using 3D breast planning techniques rather than the conventional 2D approach. These ongoing improvements and developments in radiotherapy treatment planning are leading to treatments which offer both better tumour volume coverage, and are minimising the risk of treatment-related complications. In time, these changes should allow the escalation in dose delivered to the tumour volume with the potential for increased cure rates.

Risk of cardiac death after adjuvant radiotherapy for breast cancer

BACKGROUND

Women with breast cancer who are treated with adjuvant radiation have a decreased risk of local recurrence but an increased risk of mortality from ischemic heart disease. Patients with left-sided breast tumors receive a higher dose of radiation to the heart than patients with right-sided tumors. Because radiation techniques have improved over time, we investigated whether the risk of death from ischemic heart disease after adjuvant breast radiotherapy decreased over time.

METHODS

We used the 12-registry 1973-2000 dataset from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program. Women (n = 27,283) treated with adjuvant radiation for breast cancer diagnosed in 1973-1989 were included in the study. Ischemic heart disease mortality was calculated at 15 years and compared for women diagnosed during 1973-1979, 1980-1984, and 1985-1989. Cox proportional hazards models were used to calculate the hazard of death from ischemic heart disease for women diagnosed 1973-1988 and censored at 12 years. All statistical tests were two-sided.

RESULTS

There were no differences in age, race/ethnicity, disease stage, or follow-up time between the 13 998 women with left-sided and 13 285 with right-sided cancer. For women diagnosed in 1973-1979, there was a statistically significant difference in 15-year mortality from ischemic heart disease between patients with left-sided (13.1%, 95% confidence interval [CI] = 11.6 to 14.6) and those with right-sided (10.2%, 95% CI = 8.9 to 11.5) breast cancer (P = .02); no such difference was found for women diagnosed in 1980-1984 (9.4%, [95% CI = 8.1 to 10.6] versus 8.7% [95% CI = 7.4 to 10.0], respectively, P = .64) or 1985-1989 (5.8% [95% CI = 4.8 to 6.8] versus 5.2% [95% CI = 4.4 to 5.9], respectively, P = .98). In the Cox model, the hazard ratio [HR] for ischemic heart disease mortality for women with left-sided versus women with right-sided disease was 1.50 (95% CI = 1.19 to 1.87) in 1979. With each succeeding year after 1979, the hazard of death from ischemic heart disease for women with left-sided versus those with right-sided disease declined by 6% (HR = 0.94, 95% CI = 0.91 to 0.98).

CONCLUSIONS

Risk of death from ischemic heart disease associated with radiation for breast cancer has substantially decreased over time.

Risk of cardiac death after adjuvant radiotherapy for breast cancer

BACKGROUND

Women with breast cancer who are treated with adjuvant radiation have a decreased risk of local recurrence but an increased risk of mortality from ischemic heart disease. Patients with left-sided breast tumors receive a higher dose of radiation to the heart than patients with right-sided tumors. Because radiation techniques have improved over time, we investigated whether the risk of death from ischemic heart disease after adjuvant breast radiotherapy decreased over time.

METHODS

We used the 12-registry 1973-2000 dataset from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program. Women (n = 27,283) treated with adjuvant radiation for breast cancer diagnosed in 1973-1989 were included in the study. Ischemic heart disease mortality was calculated at 15 years and compared for women diagnosed during 1973-1979, 1980-1984, and 1985-1989. Cox proportional hazards models were used to calculate the hazard of death from ischemic heart disease for women diagnosed 1973-1988 and censored at 12 years. All statistical tests were two-sided.

RESULTS

There were no differences in age, race/ethnicity, disease stage, or follow-up time between the 13 998 women with left-sided and 13 285 with right-sided cancer. For women diagnosed in 1973-1979, there was a statistically significant difference in 15-year mortality from ischemic heart disease between patients with left-sided (13.1%, 95% confidence interval [CI] = 11.6 to 14.6) and those with right-sided (10.2%, 95% CI = 8.9 to 11.5) breast cancer (P = .02); no such difference was found for women diagnosed in 1980-1984 (9.4%, [95% CI = 8.1 to 10.6] versus 8.7% [95% CI = 7.4 to 10.0], respectively, P = .64) or 1985-1989 (5.8% [95% CI = 4.8 to 6.8] versus 5.2% [95% CI = 4.4 to 5.9], respectively, P = .98). In the Cox model, the hazard ratio [HR] for ischemic heart disease mortality for women with left-sided versus women with right-sided disease was 1.50 (95% CI = 1.19 to 1.87) in 1979. With each succeeding year after 1979, the hazard of death from ischemic heart disease for women with left-sided versus those with right-sided disease declined by 6% (HR = 0.94, 95% CI = 0.91 to 0.98).

CONCLUSIONS

Risk of death from ischemic heart disease associated with radiation for breast cancer has substantially decreased over time.

Reduction of radiotherapy-induced late complications in early breast cancer: the role of intensity-modulated radiation therapy and partial breast irradiation

Radiotherapy after conservation surgery has been proven to decrease local relapse and death from breast cancer, and is now firmly established in the management of early breast carcinoma. Currently, the challenge is to minimise the morbidity caused by this treatment without losing its efficacy. This review will be divided into two parts, with Part I focusing on the radiation factors contributing to late normal tissue complications after radiotherapy for early breast cancer. Three major normal tissue side-effects will be discussed: cosmetic outcome, cardiac complications and pulmonary side-effects.

Cardiac chamber and coronary artery doses associated with postmastectomy radiotherapy techniques to the chest wall and regional nodes

PURPOSE

To compare the estimated radiation doses delivered to the cardiac chambers (CC) and coronary arteries (CA) for 5 postmastectomy radiotherapy (PMRT) techniques.

METHODS AND MATERIALS

A dosimetry study of 20 left-sided PMRT cases was conducted. Cardiac chambers (left and right atria [LA/RA] and left and right ventricles [LV/RV]) and coronary vessels (left main [LM], left anterior descending [LAD], left circumflex [LCX], right coronary [RCA] and posterior descending [PDA] arteries) were contoured on contrast-enhanced CT scans and verified by a cardiologist (T.K.). Five PMRT techniques were applied to each case; 50 Gy in 2 Gy fractions was delivered to the chest wall +/- internal mammary node targets. The techniques were: (1) standard tangents (TAN); (2) cobalt (Co); (3) reverse hockey stick (RHS); (4) mixed photon/electron beam (20/80); and (5) partially wide tangent fields (PWTF). Three-dimensional dose calculations for 100 plans were performed for all structures. Plans were compared by using the mean dose (Dmean) and the volume that received more than 30 Gy (V(30)) and 45 Gy (V(45)) for each structure.

RESULTS

Cobalt and 20/80 techniques delivered higher Dmeans to the whole heart and individual cardiac chambers (RA, RV, LA, and LV) as compared with the other three techniques. The heart received a Dmean of 21.03 +/- 3.5 Gy from Co and 11.87 +/- 5.22 Gy from 20/80. The remaining techniques delivered heart Dmeans of 2.90-4.94 Gy. When V(30) was used as a metric, all techniques had comparably low V(30) to the heart, except for Co, which resulted in a significantly higher irradiated volume of right-sided cardiac chambers (59.06% +/- 30.7 for RA F-test < 0.0001; and 61.46% +/- 22.13 for RV, F-test < 0.0001). Dmean to the proximal LAD (LAD_p) was significantly higher for RHS (17.64 +/- 7.43 Gy) and 20/80 (20.52 +/- 8.36 Gy) and lowest for PWTF (9.5 +/- 4.16 Gy). The Dmean for the distal LAD (LAD_d) was significantly lower with PWTF (11.02 +/- 7.34 Gy) than with all other techniques, including TAN (p < 0.0001). Similar results for PWTF and TAN were observed when V30 and V45 were used.

CONCLUSIONS

Cardiac substructures receive the most radiation exposure after PMRT with CO, 20/80 or both and least exposure with PWTF. Although TAN resulted in significant sparing of the majority of the cardiac structures, a significantly higher dose and volume of LAD was exposed when compared with PWTF. Although the clinical relevance of these dose differences is not clearly understood, these dosimetric estimates can serve as a baseline in the development of new techniques for locoregional treatment that will further reduce cardiac exposure.

Postmastectomy CT-based electron beam radiotherapy: Dosimetry, efficacy, and toxicity in 118 patients

PURPOSE

To evaluate the technique, dosimetry, acute and late toxicity, local control (LC), and overall survival (OS) with the use of computed tomography (CT)-based postmastectomy electron beam therapy (PMEBT) in high-risk patients.

METHODS AND MATERIALS

From 1990 to 2000, 118 patients with pathologic stage I-IIIB breast cancer underwent PMEBT of the chest wall (CW) (n = 3), CW and supraclavicular fossa (SCV) (n = 63), CW, SCV, and internal mammary lymph nodes (IMN) (n = 51), and SCV+IMN (n = 1). Radiation therapy was delivered with an en face electron beam with a custom cutout. Treatment plans were all CT-based. The plans of 16 patients were retrospectively reviewed to analyze dosimetry data. A retrospective chart review was conducted to assess acute and late complications, LC, and OS.

RESULTS

At a median follow-up of 43 months, 5-year LC and OS were 91% and 61%, respectively. Sixty-one patients developed acute grade 3-4 skin toxicity, necessitating treatment breaks in 33 patients. Fifteen patients experienced a worsening of lymphedema, and 2 patients developed cardiac injury thought to be unrelated to radiotherapy. No patients developed symptomatic pneumonitis. Dosimetric analysis revealed heart and lung normal tissue complication probabilities of zero. Analysis of other clinically relevant dosimetric parameters revealed PMEBT to be comparable to previously reported techniques.

CONCLUSION

Postmastectomy electron beam therapy is an effective way to deliver radiation to the postmastectomy chest wall and adjacent nodal sites. It offers acceptable acute and late toxicities and a high degree of local control given the high-risk population to which it is offered.

Breast cancer: improving outcome following adjuvant radiotherapy

In the treatment of early breast cancer adjuvant irradiation improves local control following both mastectomy and breast-conserving surgery. For women at high risk of relapse it also increases survival. Breast radiotherapy is usually given using simple planning techniques and serious morbidity is unusual. The greatest concern following adjuvant breast irradiation is of an increase in cardiovascular mortality after 15-20 years. New techniques of breast irradiation including conformal radiotherapy and intensity-modulated radiotherapy (IMRT) have been shown to reduce cardiac and lung irradiation. In addition, improved dosimetry within the breast may improve both local control and cosmesis. To replace current radiotherapy techniques with those requiring more complex planning would demand an increase in resources including both machinery and staff. In this review we outline the indications and benefits of breast radiotherapy along with the planning process. Technical advances are discussed within the context of improving outcome at a time of limited national resources.

Adjuvant radiotherapy for breast cancer: effects of longer follow-up

BACKGROUND AND PURPOSE

Recent and large trials of adjuvant radiotherapy for breast cancer have shown an overall survival benefit in favour of radiotherapy. However, with longer follow-up the late lethal toxicity of radiotherapy might reduce the overall survival benefits. In this paper we investigate more deeply this hypothesis.

PATIENTS AND METHODS

Overviews of the Early Breast Cancer Trialists' Collaborative Group provide uniform data on more than 50 unconfounded trials on adjuvant radiotherapy for early breast cancer. These data were published at regular intervals: 1987, 1990, 1995, and 2000. The odds ratios (death of any cause) were borrowed to compare the benefits of adjuvant radiotherapy between the early publications and the more mature data of the same trials. Statistical significance is calculated following logrank statistics. The comparison of odds ratios (radiotherapy versus surgery only) was done for the whole group of trials, for the older (patients accrual started in 1970 or earlier) and the more recent trials (patient accrual started after 1970), and for the large (>or=600 patients) and the small trials (<600 patients).

RESULTS

Comparison of early with more mature data reveals that the odds ratios for overall survival remain stable as data become more mature. The analyses of trials' age and trials' size, as predictors of overall survival benefit, indicate that these factors become statistically more significant with increasing maturity of the trials. In the large recent trials an overall survival benefit due to radiotherapy (odds reduction) of 10, 10, 12 and 13%, respectively P<0.3, 0.2, 0.005 and 0.00005 is found in the successive publications. The difference in survival benefit of radiotherapy between the group of large recent trials and group of old or small trials becomes more significant at the successive updates: 10 via 9% and 12 to 13% (odds reductions), with respectively P=0.2, 0.2, 0.004 and 0.00005.

CONCLUSIONS

These results support the hypothesis that the survival benefit in the recent trials is an inherent characteristic of the recent and large trials, not influenced by follow-up duration. The effect of radiotherapy as performed in the large recent trials is clinically and statistically significantly different from the effect of radiotherapy in the old or small trials. As a consequence, predictions based on pooled data including old radiotherapy trials should not be extrapolated to modern radiotherapy.

Radiation-induced cardiomyopathy as a function of radiation beam gating to the cardiac cycle

Portions of the heart are often unavoidably included in the primary treatment volume during thoracic radiotherapy, and radiation-induced heart disease has been observed as a treatment-related complication. Such complications have been observed in humans following radiation therapy for Hodgkin's disease and treatment of the left breast for carcinoma. Recent attempts have been made to prevent re-stenosis following angioplasty procedures using external beam irradiation. These attempts were not successful, however, due to the large volume of heart included in the treatment field and subsequent cardiac morbidity. We suggest a mechanism for sparing the heart from radiation damage by synchronizing the radiation beam with the cardiac cycle and delivering radiation only when the heart is in a relatively hypoxic state. We present data from a rat model testing this hypothesis and show that radiation damage to the heart can be altered by synchronizing the radiation beam with the cardiac cycle. This technique may be useful in reducing radiation damage to the heart secondary to treatment for diseases such as Hodgkin's disease and breast cancer.

Irradiation of the heart during tangential breast treatment: a study within the START trial

Radiotherapy to the breast is often given as a component of the treatment for women with breast cancer. It has been shown to increase overall survival although an increase in cardiac mortality has also been noted. This study was undertaken as part of the START trial quality assurance programme to record and evaluate the cardiac dose using modern radiotherapy techniques. Departments randomizing patients into the START trial and who had CT facilities for planning breast patients were invited to take part. 62 patients were included. CT slices were taken at the level of the maximum heart depth and on the treatment field central axis. Each patient was planned in the normal way and the distributions were analysed by the quality assurance team at Mount Vernon Hospital. The maximum heart position was found to be inferior to the central axis used for breast planning for the majority of patients; mean position 2.3 cm inferior with a mean maximum heart depth of 0.55 cm. For 45% of patients the maximum heart dose was less than 50% of the prescribed dose. The study showed that the volume of irradiated cardiac tissue has decreased compared with earlier studies, and also highlighted the need to scan away from the central axis if the dose to cardiac tissue is to be assessed.

Postoperative radiotherapy after conservative surgery for early breast cancer: 5-year results

BACKGROUND: Breast conserving surgery followed by postoperative radiotherapy, as alternative to radical mastectomy, has been accepted as an optimal method for loco- regional treatment of the majority of women with early stage of breast carcinoma. The aim of the study was to evaluate the results of postoperative radiotherapy after breast conserving surgery in the Institute for oncology and radiology of Serbia. METHODS: During the 3-year period, 109 breast cancer patients with stage I and II were treated with postoperative radiotherapy after breast conserving surgery. Ninety- four patients underwent quadrantectomy with axillary node dissection, and 15 patients underwent only tumorectomy. After surgery all patients received postoperative radiotherapy to the whole breast with tumor dose 50 Gy in 15 fractions every second day. In 52 patients radiotherapy was given to the regional lymphatics with tumor dose 45 Gy in 15 fractions every second day. Twenty-eight patients received a booster dose (10 Gy) to the tumor bed. Adjuvant systemic therapy was administered depending on the nodal involvement and steroid receptors content: 17 patients received adjuvant chemotherapy (CMF or FAC), 18 received adjuvant hormonal therapy (tamoxifen or ovarian ablation), and 6 patients received both chemo- and hormonotherapy. RESULTS: After median follow-up period of 62 months, there was no evidence of loco- regional recurrence in anyone of patients. Distant metastases occurred in 7 patients (6.4%) with median disease free interval of 27.6 months. At last follow-up 91 patients (83.4%) were alive, 4 patients (3.7%) were dead of disease, and the same number was dead of other causes. The 5-year overall survival rate was 92.9% and disease-free survival rate was 92.7%. CONCLUSION: According to our results the combined surgery and radiotherapy approach provides good local control of early breast cancer patients. Postoperative radiotherapy after breast conserving surgery with or without adjuvant systemic therapy has important role in adjuvant treatment of early breast cancer.

Phantom study of radiation doses outside the target volume brachytherapy versus external radiotherapy of early breast cancer

BACKGROUND AND PURPOSE

Brachytherapy is sometimes suggested as an adjuvant treatment after surgery of some tumours. When introducing this, it would be useful to have an estimate of the dose distribution to different body sites, both near and distant to target, comparing conventional external irradiation to brachytherapy. The aim of the present study was to determine radiation doses with both methods at different body sites, near and distant to target, in an experimental situation on an operated left sided breast cancer on a female Alderson phantom.

METHODS

Five external beam treatments with isocentric tangential fields were given by a linear accelerator. A specified dose of 1.0 Gy was given to the whole left sided breast volume. Five interstitial brachytherapy treatments were given to the upper, lateral quadrant of the left breast by a two plane, 10 needles implant. A dose of 1.0 Gy specified according to the Paris system was administered by a pulsed dose rate afterloading machine. Absorbed dose in different fixed dose points were measured by thermoluminescence dosimeters.

RESULTS

Both methods yielded an absorbed dose of the same size to the bone marrow and internal organs distant to target, 1.0-1.4% of the prescribed dose. There was a trend of lower doses to the lower half of the trunk and higher doses to the upper half of the trunk, respectively, by brachytherapy. A 90% reduction of absorbed dose with brachytherapy compared to external irradiation was found in the near-target region within 5 cm from target boundary where parts of the left lung and the heart are situated. If an adjuvant dose of 50 Gy is given with the external radiotherapy and brachytherapy, the absorbed dose in a part of the myocardium could be reduced from 31.8 to 2.1 Gy.

CONCLUSIONS

Near target, brachytherapy yielded a considerably lower absorbed dose which is of special importance when considering radiation effects on the myocard and lungs. We could not demonstrate any difference of importance, in absorbed dose to dose points distant to target.

Can virtual simulation of breast tangential portals accurately predict lung and heart volumes?

A treatment portal or simulator image has traditionally been used to demonstrate the lung and heart coverage of the breast tangential portal. In many cases, these images were acquired as a planning session on the linear accelerator. The patients were also CT scanned to assess the lung/heart volume and to determine the surgical site depth for the electron-boost energy. A study using 50 consecutive patients was performed comparing the digitally reconstructed radiograph (DRR) from the virtual simulation with treatment portal images. Modification to the patient's arm position is required when performing the planning CT scans due to the aperture size of the CT scanner. Virtual simulation was used to assess the potential variation of lung and heart measurements. The average difference in lung volume between the DRR and portal image was less than 2 mm, with a range of 0-5 mm. Arm position did not have a significant impact on field deviation; however, great care was taken to minimize any changes in arm position. The modification of the arm position for CT scanning did not lead to significant variations between the DRRs and portal images. The Advantage Sim software has proven capable of producing good quality DRR images, providing a realistic representation of the lung and heart volume included in the treatment portal.