Identification and characterization of myocardial metastases in neuroendocrine tumor patients using 68Ga-DOTATATE PET-CT

Background: Focal 68Ga-DOTATATE PET lesions within the myocardium of neuroendocrine tumor (NET) patients are observed in clinical practice. We determined the frequency and characteristics of lesions that are consistent with cardiac metastasis and assessed the lesion detection rate of conventional imaging. Methods: 629 patients who underwent 68Ga-DOTATATE PET-CT at a supraregional comprehensive cancer center on NET were included from a consecutive registry. Inclusion criteria were: (1) focal 68Ga-DOTATATE tracer uptake within the myocardium in more than two sequential PET exams, and (2) contrast-enhanced CT. To determine the diagnostic accuracy of conventional CT imaging, a case-control cohort with a ratio of 1:3 was used. PET and CT were independently analyzed by two blinded readers. Cohen's K was assessed for interreader agreement Descriptive statistics were applied for frequencies and characteristics and group comparisons were analyzed using the Fisher's exact test. Results: The prevalence of myocardial metastases related to the registry was 2.4% (15 of 629 NET patients fulfilling the inclusion criteria), for a total of 21 myocardial 68Ga-DOTATATE foci detected. Myocardial lesions were most frequently located in the left ventricle (43%) and the septum (43%). No patient demonstrated a pericardial effusion. Patients with myocardial metastases did not differ in demographics, tumor grading, disease stage or circulating tumor markers compared to the overall registry (all p > 0.05). Higher Ki67-Indices were observed (p = 0.049) for patients with myocardial metastases. Interreader agreement for PET assessment was excellent (Cohen's K = 1.0). CT reading showed a sensitivity of 19% (95% confidence interval: 6-43%) at a specificity of 100% (95% confidence interval: 90-100%). Conclusions: 68Ga-DOTATATE PET enables detection of myocardial metastatic lesions in NET patients. In contrast, standard morphologic CT imaging provides very limited sensitivity.