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

https://doi.org/10.1016/j.ijrobp.2006.06.007Get rights and content

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.

Introduction

Positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) is considered to be useful for evaluating tumor extension or detecting recurrence in patients with esophageal cancer. Therefore, FDG-PET is a promising noninvasive method for follow-up after chemoradiotherapy for esophageal cancer. Some patients have shown focal increased FDG uptake in the basal myocardium after completion of chemoradiotherapy. We suspected that these findings indicate myocardial damage induced by radiotherapy.

Before the 1960s, the myocardium was considered to be a relatively radiation-resistant organ, although pericardiac effusion without symptoms after irradiation for the mediastinum often occurred. Recently, however, there have been many reports of patients with radiation-induced myocardial damage in the late phase (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16). There have also been reports of occasional heart-related deaths in patients with esophageal cancer after radiotherapy (17, 18). Significant impairment of the left ventricular ejection fraction after radiotherapy for the mediastinum has also been reported (19). In addition, ischemic changes in the irradiated myocardium have been observed in some studies on myocardial perfusion imaging (7, 8, 9).

In the present study, we evaluated patients who showed focal increased FDG uptake in the basal myocardium after radiotherapy for esophageal cancer. To our knowledge, although we reported a case of radiation-induced cardiomyopathy (20), there are no other reports of those FDG-PET findings that suggest radiation-induced myocardial damage. To clarify the clinical significance of these findings, we investigated the relationship with dose distribution in the myocardium and compared the findings of heart ultrasound (US), magnetic resonance imaging (MRI), and myocardial single-photon emission computed tomography (SPECT).

Section snippets

Patients

Between August 2004 and July 2005, a total 64 patients (60 males and 4 females; median age, 66 years; range, 45 to 86 years) were enrolled in the present study with follow-up study for cancer. All patients had primary or postoperative recurrent thoracic esophageal cancer and had undergone irradiation to the mediastinum in our institution. Sixty-three patients had been proven to have squamous cell carcinoma, and one patient had been proven to have adenocarcinoma. The characteristics of all

Results

In the present study, 13 (20.3%) of the 64 patients showed high FDG uptake in the base of the left ventricular myocardium corresponding to the irradiated fields in comparison with FDG uptake in the myocardium outside the irradiated fields. The distribution of high FDG uptake is very characteristic and not consistent with the vascular territory of coronal arteries. That is, the high FDG uptake was seen in the basal portions of the anterior wall, posterior wall, lateral wall, and interventricular

Discussion

In the present study, 13 (20.3%) of the 64 patients who underwent irradiation for esophageal cancer showed high FDG uptake in the basal myocardium. The regions of high FDG uptake corresponded to the irradiated field but not to any coronary artery vascular territories. It is unlikely that these findings are a result of regional ischemia due to stenosis or occlusion of coronary arteries. Therefore, in this study, we explored the possibility of myocardial damage induced by radiation.

Myocardial

Conclusions

Focal increased FDG uptake in the basal myocardium is sometimes seen in patients with esophageal cancer after radiotherapy. This finding might indicate radiation-induced myocardial damage. Cardiac function and symptom of the patients with those focal increased FDG uptake should be followed to prevent cardiac impairment or death as a result of radiation therapy.

References (22)

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