Myocardial Metastases of Carcinoid Visualized by 18F-Dihydroxy-Phenyl-Alanine Positron Emission Tomography
Carcinoids are rare tumors arising from neuroendocrine cells that can produce and secrete hormones. Carcinoid disease may include cardiac involvement, with right-sided endocardial and valvular fibrous lesions of the heart.1 This so-called carcinoid heart disease may present with cardiac failure and arrhythmias. More uncommonly, myocardial metastases are diagnosed in carcinoid disease. The reported incidence of myocardial carcinoid metastases among patients with metastatic carcinoid disease is 4%.2 These metastases usually are discovered during screening for distant metastatic disease or carcinoid heart disease but also may present with arrhythmias. However, the incidence may be underestimated as a consequence of limited resolution of the imaging techniques used. In the past, myocardial metastases have been located with ultrasonography and somatostatin receptor scintigraphy (SRS). Lesions <1.0 cm are difficult to identify with ultrasonography, and although good sensitivity (92%) has been reported for SRS, it is by no means perfect.3,4 New imaging techniques such as the 18F-dihydroxy-phenyl-alanine (18F-DOPA) positron emission tomography (PET) scan can be of additional value in diagnosing these rare metastases of carcinoid disease, as shown in the following case report.
A 60-year-old man presented with diarrhea, abdominal pain, and weight loss but no cardiac complaints. Physical examination revealed no abnormalities apart from a slight hepatomegaly. Laboratory values showed mild anemia, an elevated serotonin level in platelets of 41 nmol/109 platelets (upper reference limit, 5.4 nmol/109 platelets), and a urinary 5-hydroxyindoleacetic acid level of 15.2 mmol/mol creatinine (upper reference limit, 3.8 mmol/mol creatinine).
SRS with planar imaging of the whole body and single-photon-emission computed tomography imaging of the abdomen and chest 24 hours after injection of 200 MBq 111In-octreotide showed uptake in the abdomen, bones, ribs, and left supraclavicular region (Figure 1A). An 18F-DOPA PET scan revealed uptake in the abdomen, bone metastases, and 2 lesions in the heart (Figure 1B and Movie 1 in the online Data Supplement). The ECG showed a sinus bradycardia of 52 bpm during metoprolol for hypertension but was otherwise normal (Figure 2). Echocardiography showed no tumor lesions and no abnormalities of right ventricular function or valves indicative of carcinoid heart disease.
An MRI of the heart demonstrated 2 myocardial lesions in the left ventricle. Fusion of 18F-DOPA PET and magnetic resonance imaging (MRI) confirmed the presence of 2 lesions in the left ventricular myocardium (Figure 3A). In retrospect, 1 myocardial lesion also was visible on SRS (Figure 3B; fusion of MRI and SRS). Given the absence of cardiac problems, no surgical intervention was considered for the cardiac lesions. The primary ileal tumor was surgically removed and confirmed to be a carcinoid. Follow-up 18F-DOPA PET and MRI scans 1 year later showed unchanged metastases, including the cardiac lesions and no new metastases.
PET scanning using the catecholamine precursor 18F-DOPA was recently shown to be of diagnostical value in carcinoid disease. Imaging with 18F-DOPA is based on the intrinsic property of neuroendocrine tumors to take up amine precursors such as 18F-DOPA. The combination of this specific tracer with the high resolution provided by PET shows an excellent sensitivity of detection of neuroendocrine tumor lesions (up to 96%), which is higher than the sensitivity with SRS in carcinoid patients.4 This can be explained by the limited spatial resolution and the lack of somatostatin receptor expression in a number of tumors. Consequently, in carcinoid patients with cardiac complaints, an 18F-DOPA PET scan should be considered to demonstrate or rule our myocardial metastases.
The treatment for myocardial metastases usually consists of watchful waiting or surgical removal. Recently, a case of successful external beam irradiation has been reported. In our patient, an absence of complaints and stable cardiac lesions justify watchful waiting.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/cgi/content/full/118/15/e1602/DC1.
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