Evaluation of radiation-induced myocardial damage using iodine-123 β-methyl-iodophenyl pentadecanoic acid scintigraphy

Preliminary results of reduced myocardial blood flow in the subacute phase after radiation therapy for thoracic esophageal cancer: A quantitative analysis with stress dynamic myocardial computed tomography perfusion imaging

BACKGROUND AND PURPOSE

Late adverse cardiac events after radiation therapy (RT) for thoracic malignancies are known, but the underlying mechanisms are poorly understood. This study aimed to determine the radiation dose that can cause MBF alterations in the subacute phase after RT for thoracic esophageal cancer using stress dynamic myocardial computed tomography perfusion imaging (CTP).

MATERIALS AND METHODS

Twenty-five patients with esophageal cancer scheduled for RT were prospectively enrolled. The quantitative analysis of MBF by CTP was performed before and 3 months after RT. The mean radiation dose and hyperemic MBF in 15 segments of the left ventricular (LV) myocardium were determined. ΔMBF was calculated in each segment as MBFafter RT - MBFbeforeRT. The myocardial segments were classified into the following 5 groups according to the mean radiation dose: group A, <10 Gy; B1, 10-15 Gy; B2, 15-20 Gy; C, 20-30 Gy; and D, >30 Gy.

RESULTS

The final cohort included 22 patients who completed pre- and post-RT CTP. A one-way analysis of variance revealed a significant difference (p=0.005) in ΔMBF among the five groups of LV segments classified by the mean radiation dose. ΔMBF was significantly lower in group C (-7.7 ± 28.9 mL/min/100 g, p=0.020) and group D (-8.4 ± 34.8 mL/min/100 g, p=0.004) in comparison to ΔMBF in group A (4.9 ± 26.1 mL/min/100 g).

CONCLUSIONS

This study using CTP early after RT demonstrated a significant reduction of the MBF in the LV segments with ≥20 Gy of radiation. The results might provide important insights into preventing radiotherapy-induced cardiac events.

Evaluation of the dosimetric impact of heart function-based volumetric modulated arc therapy planning in patients with esophageal cancer

Radiotherapy for esophageal cancer entails high-dose irradiation of the myocardium owing to its close anatomical proximity to the esophagus. This study aimed to evaluate the dosimetric impact of functional avoidance planning for the myocardium with volumetric-modulated arc therapy (VMAT) in patients with esophageal cancer and determine the feasibility of functional planning. Ten patients with early stage esophageal cancer were included in this study. The prescribed dose was 60 Gy administered in 30 fractions. An experienced physician contoured the left ventricle (LV) of the myocardium. For each patient, an anatomical plan (non-LV-sparing plan) and a functional plan (LV-sparing plan) were created using the VMAT. In the functional plan, the mean percentage of LV volume receiving a dose of ≥ 30 and ≥ 40 Gy was 6.0% ± 6.7% and 2.4% ± 2.7%, respectively, whereas in the anatomical plan, they were 11.7% ± 13.1% and 4.9% ± 6.5%, respectively. There were no significant differences with respect to the dose to the hottest 1 cm³ of the planning target volume (PTV) and the minimum dose of the gross tumor volume and the dosimetric parameters of other normal tissues between the anatomical and functional plans. We compared the anatomical and functional plans of patients with esophageal cancer undergoing VMAT. Our results demonstrated that the functional plan reduced the dose to the LV with no significant differences in the organs at risk and PTV, indicating that avoidance planning can be safely performed when administering VMAT in patients with esophageal cancer.

Dose-Dependent Radiation-Induced Myocardial Damage in Esophageal Cancer Treated With Chemoradiotherapy: A Prospective Cardiac Magnetic Resonance Imaging Study

Purpose

The purpose of this prospective study was to evaluate radiation-induced myocardial damage after mediastinal radiation therapy (RT) using late gadolinium-enhancement (LGE) magnetic resonance imaging (MRI).

Methods and Materials

We enrolled 19 patients with esophageal cancer who were expected to have long-term survival by definitive treatment. They underwent delayed contrast-enhanced MRI (19 patients before treatment, 19 patients 6 months after treatment, and 12 patients 1.5 years after treatment). Dose distribution of the left ventricle was made using computed tomography, and the dose volume histogram of the left ventricle was calculated. Myocardial signal intensities in individual MRIs were normalized by the mean values in regions receiving low doses (<5 Gy). Changes in the normalized signal intensities after mediastinal radiation therapy were compared among regions where irradiation doses were 0 to 10 Gy, 10 to 20 Gy, 20 to 30 Gy, 30 to 40 Gy, 40 to 50 Gy, and 50 to 60 Gy, and we investigated whether intensity change was detected in a dose-dependent manner.

Results

The registered patients were treated with concurrent chemoradiotherapy with a median total dose of 60 Gy (50.4-66 Gy). Chemotherapy consisting of cisplatin and 5-fluorouracil was administered. In the population-based dose-response curve, dose-dependent intensity changes progressively increased in regions receiving more than 30 Gy. The averages of relative intensity change at 6 months and 1.5 years after treatment were 1.1% and −1.9% at 20 to 30 Gy and 37.5% and 17.5% at 40 to 50 Gy, respectively. LGE in regions receiving more than 30 Gy was detected in 68% (13/19) of the patients.

Conclusions

A dose-dependent relationship for myocardial signal intensity change was found by using LGE MRI. It may be necessary to reduce the volume of the myocardium receiving more than 30 Gy.

Metabolic Changes Precede Radiation-Induced Cardiac Remodeling in Beagles: Using Noninvasive 18F-FDG (18F-Fludeoxyglucose) and 13N-Ammonia Positron Emission Tomography/Computed Tomography Scans

Background

This study was performed to characterize the metabolic, functional, and structural cardiac changes in a canine model of radiation‐induced heart disease by serial in vivo imaging and ex vivo analyses.

Methods and Results

Thirty‐six dogs were randomly assigned to control or irradiated groups at 3 time points (months 3, 6, and 12 after radiation; each group comprised 6 dogs). The left anterior myocardium of dogs in irradiated groups was irradiated locally with a single dose of 20‐Gy X‐ray. The irradiated myocardial regions showed increased myocardial uptake of ¹⁸F‐FDG (¹⁸F‐fludeoxyglucose) in the irradiated beagles, but the increased uptake area decreased at months 6 and 12 compared with month 3 after radiation. Abnormality of myocardial perfusion and cardiac function were detected at month 6 after radiation. Compared with the control groups, the protein expression of GLUT4 (glucose transporter 4) was upregulated in the irradiated groups, correlating with significantly decreased CPT1 (carnitine acyltransferase 1) expression. Mitochondria degeneration, swelling, and count reduction in the irradiated groups were observed. The difference in CD68 of macrophage markers and the inflammatory cytokines (IL‐6 [interleukin 6], TNF‐α [tumor necrosis factor α]) between the irradiation and control groups was not significant. Furthermore, the progressive aggravation of apoptosis and fibrosis was displayed.

Conclusions

Elevated ¹⁸F‐FDG uptake occurred after irradiation and subsequently led to ventricular perfusion defects and dysfunction. The process was associated with myocardial metabolic substrate remodeling, cardiac muscle cell apoptosis, and myocardial fibrosis rather than inflammation.

Effect of long fasting on myocardial accumulation in 18F-fluorodeoxyglucose positron emission tomography after chemoradiotherapy for esophageal carcinoma

This study sought to evaluate the effect of fasting time prior to 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) on myocardial accumulation of FDG in patients receiving radiotherapy for esophageal carcinoma, and the spatial relationship between the irradiated dose and myocardial accumulation of FDG. Forty-one patients with thoracic esophageal carcinoma received FDG-PET with <18-h (24 patients) or ≥18-h (17 patients) fasting status. Their myocardial accumulation patterns of FDG were categorized using the maximal standardized uptake value (SUVmax) into three types: physiological, focal and no pathological accumulation. The incidence rates of each pattern were then compared using the Fisher's exact test between two types of fasting, ≥18-h and <18-h, prior to FDG-PET. Additionally, the left ventricle was defined using four subsites depending on the irradiated doses, and the SUVmax values were compared among the subsites using the Kruskal-Wallis test. The incidence of the physiological accumulation pattern decreased significantly more in the ≥18-h fasting status group than in the <18-h fasting group (18% versus 71%, P = 0.002), and the focal accumulation of FDG was detected at a significantly higher rate (65% versus 13%, P = 0.001). The left ventricular subsites receiving the higher doses showed significantly higher SUVmax values than did the subsites receiving the lower doses (P < 0.001). In conclusion, radiotherapy was associated with abnormal myocardial accumulation of FDG. Long fasting for 18 h or more prior to FDG-PET would be useful in detecting subsequent myocardial damage from chemoradiotherapy compared with <18-h fasting prior to FDG-PET.

The Impact of Cardiac Radiation Dosimetry on Survival After Radiation Therapy for Non-Small Cell Lung Cancer

PURPOSE

The heart receives high radiation doses during radiation therapy of advanced-stage lung cancer. We have explored associations between overall survival, cardiac radiation doses, and electrocardiographic (ECG) changes in patients treated in IDEAL-CRT, a trial of isotoxically escalated concurrent chemoradiation delivering tumor doses of 63 to 73 Gy.

METHODS AND MATERIALS

Dosimetric and survival data were analyzed for 78 patients. The whole heart, pericardium, AV node, and walls of left and right atria (LA/RA-Wall) and ventricles (LV/RV-Wall) were outlined on radiation therapy planning scans, and differential dose-volume histograms (dDVHs) were calculated. For each structure, dDVHs were approximated using the average dDVH and the 10 highest-ranked structure-specific principal components (PCs). ECGs at baseline and 6 months after radiation therapy were analyzed for 53 patients, dichotomizing patients according to presence or absence of "any ECG change" (conduction or ischemic/pericarditis-like change). All-cause death rate (DR) was analyzed from the start of treatment using Cox regression.

RESULTS

38% of patients had ECG changes at 6 months. On univariable analysis, higher scores for LA-Wall-PC6, Heart-PC6, "any ECG change," and larger planning target volume (PTV) were significantly associated with higher DR (P=.003, .009, .029, and .037, respectively). Heart-PC6 and LA-Wall-PC6 represent larger volumes of whole heart and left atrial wall receiving 63 to 69 Gy. Cardiac doses ≥63 Gy were concentrated in the LA-Wall, and consequently Heart-PC6 was highly correlated with LA-Wall-PC6. "Any ECG change," LA-Wall-PC6 scores, and PTV size were retained in the multivariable model.

CONCLUSIONS

We found associations between higher DR and conduction or ischemic/pericarditis-like changes on ECG at 6 months, and between higher DR and higher Heart-PC6 or LA-Wall-PC6 scores, which are closely related to heart or left atrial wall volumes receiving 63 to 69 Gy in this small cohort of patients.

Radiation-induced heart disease in lung cancer radiotherapy: A dosimetric update

BACKGROUND

Radiation-induced heart disease (RIHD), which affects the patients' prognosis with both acute and late side effects, has been published extensively in the radiotherapy of breast cancer, lymphoma and other benign diseases. Studies on RIHD in lung cancer radiotherapy, however, are less extensive and clear even though the patients with lung cancer are delivered with higher doses to the heart during radiation treatment.

METHODS

In this article, after extensive literature search and analysis, we reviewed the current evidence on RIHD in lung cancer patients after their radiation treatments and investigated the potential risk factors for RIHD as compared to other types of cancers.

RESULT

Cardiac toxicity has been found highly relevant in lung cancer radiotherapy. So far, the crude incidence of cardiac complications in the lung cancer patients after radiotherapy has been up to 33%.

CONCLUSION

The dose to the heart, the lobar location of tumor, the treatment modality, the history of heart and pulmonary disease and smoking were considered as potential risk factors for RIHD in lung cancer radiotherapy. As treatment techniques improve over the time with better prognosis for lung cancer survivors, an improved prediction model can be established to further reduce the cardiac toxicity in lung cancer radiotherapy.

Association between radiation dose to the heart and myocardial fatty acid metabolic impairment due to chemoradiation-therapy: Prospective study using I-123 BMIPP SPECT/CT

PURPOSE

To investigate long term changes in myocardial fatty acid metabolic impairment caused by chemoradiation-therapy (CRT).

MATERIALS AND METHODS

We investigated 12 esophageal cancer patients who underwent SPECT/CT using I-123-labeled fatty acid analog (BMIPP) at pre-CRT, pre-boost irradiation, 3-month post-CRT, and 1-year post-CRT. The myocardial uptake was measured using the defect score and the total percentage of uptake (%uptake), which were defined as the sum of the visual scores and that of %uptake in each of 17 segments in the left ventricle (LV), respectively. The correlations between radiation dose to the heart (mean dose, V20, V40, and V60 of the LV and the whole heart (WH)) and the change of myocardial BMIPP uptake from pre-CRT (Δmyocardial BMIPP uptake) were assessed.

RESULTS

At pre-boost, Δmyocardial BMIPP uptake was significantly correlated with LV-V40 and WH-V60. At 3-month post-CRT, Δmyocardial BMIPP uptake was significantly correlated with LV-V40, WH-V40, and WH-V60. However, there were no statistically significant correlations at 1-year post-CRT. Neither mean dose nor V20 of the LV/WH was significantly correlated with Δmyocardial BMIPP uptake at any time.

CONCLUSIONS

In the long term after CRT, myocardial metabolism might be affected by factors other than the radiation dose to the heart.

Detection of Myocardial Metabolic Abnormalities by 18F-FDG PET/CT and Corresponding Pathological Changes in Beagles with Local Heart Irradiation

Objective

To determine the efficacy of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the detection of radiation-induced myocardial damage in beagles by comparing two pre-scan preparation protocols as well as to determine the correlation between abnormal myocardial FDG uptake and pathological findings.

Materials and Methods

The anterior myocardium of 12 beagles received radiotherapy locally with a single X-ray dose of 20 Gy. 18F-FDG cardiac PET/CT was performed at baseline and 3 months after radiation. Twelve beagles underwent two protocols before PET/CT: 12 hours of fasting (12H-F), 12H-F followed by a high-fat diet (F-HFD). Regions of interest were drawn on the irradiation and the non-irradiation fields to obtain their maximal standardized uptake values (SUVmax). Then the ratio of the SUV of the irradiation to the non-irradiation fields (INR) was computed. Histopathological changes were identified by light and electron microscopy.

Results

Using the 12H-F protocol, the average INRs were 1.18 ± 0.10 and 1.41 ± 0.18 before and after irradiation, respectively (p = 0.021). Using the F-HFD protocol, the average INRs were 0.99 ± 0.15 and 2.54 ± 0.43, respectively (p < 0.001). High FDG uptake in irradiation field was detected in 33.3% (4/12) of 12H-F protocol and 83.3% (10/12) of F-HFD protocol in visual analysis, respectively (p = 0.031). The pathology of the irradiated myocardium showed obvious perivascular fibrosis and changes in mitochondrial vacuoles.

Conclusion

High FDG uptake in an irradiated field may be related with radiation-induced myocardial damage resulting from microvascular damage and mitochondrial injury. An F-HFD preparation protocol used before obtaining PET/CT can improve the sensitivity of the detection of cardiotoxicity associated with radiotherapy.

Assessment of myocardial metabolic disorder associated with mediastinal radiotherapy for esophageal cancer -a pilot study

Background

To evaluate the dose-effect relations for myocardial metabolic disorders after mediastinal radiotherapy (RT) by performing iodine-123 β-methyl-iodophenyl pentadecanoic acid (I-123 BMIPP) scintigraphy.

Methods

Between 2011 and 2012, we performed I-123 BMIPP scintigraphy for patients with esophageal cancer before and six months after curative mediastinal RT. Single photon emission computed tomography (SPECT) images of pre-RT and post-RT were registered into RT dose distributions. The myocardium was contoured, and the regional RT dose was calculated. Normalization is required to compare pre- and post-RT SPECT images because the uptake pattern is changed due to the breathing level. Normalization was applied on the mean of SPECT counts in regions of the myocardium receiving less than 5 Gy. Relative values in each dose region (interval of 5 Gy) were calculated on the basis of this normalization for each patient. The reduction in the percent of relative values was calculated.

Results

Five patients were enrolled in this study. None of the patients had a past history of cardiac disease. The left ventricle was partially involved in RT fields in all patients. The patients received RT with median total doses of 60-66 Gy for the primary tumor and metastatic lymph nodes. Concomitant chemotherapy consisting of cisplatin or nedaplatin and 5-fluorouracil with RT was performed in 4 patients. All patients had reduced uptake corresponding to RT fields. Dose-effect relations for reduced uptake tended to be observed at 6 months after RT with mean decreases of 8.96% in regions at 10-15 Gy, 12.6% in regions at 20-25 Gy, 15.6% in regions at 30-35 Gy, 19.0% in regions at 40-45 Gy and 16.0% in regions at 50-55 Gy.

Conclusions

Dose-effect relations for myocardial metabolic disorders tended to be observed. We may need to make an effort to reduce high-dose mediastinal RT to the myocardium in RT planning.