Comparative evaluation of 18F-FLT and 18F-FDG for detecting cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis

Takashi Norikane; Yuka Yamamoto; Yukito Maeda; Takahisa Noma; Hiroaki Dobashi; Yoshihiro Nishiyama

doi:10.1186/s13550-017-0321-0

Comparative evaluation of ¹⁸F-FLT and ¹⁸F-FDG for detecting cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis

EJNMMI Res. 2017 Aug 29;7(1):69. doi: 10.1186/s13550-017-0321-0.

Authors

Takashi Norikane¹, Yuka Yamamoto², Yukito Maeda², Takahisa Noma³, Hiroaki Dobashi⁴, Yoshihiro Nishiyama²

Affiliations

¹ Department of Radiology, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan. t-nori@kms.ac.jp.
² Department of Radiology, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan.
³ Division of Cardiorenal and Cerebrovascular Medicine, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan.
⁴ Division of Hematology, Rheumatology and Respiratory Medicine, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan.

Abstract

Background: ¹⁸F-FDG PET has been used in sarcoidosis for diagnosis and determination of the extent of the disease. However, assessing inflammatory lesions in cardiac sarcoidosis using ¹⁸F-FDG can be challenging because it accumulates physiologically in normal myocardium. Another radiotracer, 3'-deoxy-3'-¹⁸F-fluorothymidine (¹⁸F-FLT), has been investigated as a promising PET tracer for evaluating tumor proliferative activity. In contrast to ¹⁸F-FDG, ¹⁸F-FLT uptake in the normal myocardium is low. The purpose of this retrospective study was to compare the uptake of ¹⁸F-FLT and ¹⁸F-FDG in the evaluation of cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis. Data for 20 patients with newly diagnosed sarcoidosis were examined. ¹⁸F-FLT and ¹⁸F-FDG PET/CT studies had been performed at 1 h after each radiotracer injection. The patients had fasted for at least 18 h before ¹⁸F-FDG PET/CT but were given no special dietary instructions regarding the period before ¹⁸F-FLT PET/CT. Uptake of ¹⁸F-FLT and ¹⁸F-FDG was examined visually and semiquantitatively using maximal standardized uptake value (SUVmax).

Results: Two patients had cardiac sarcoidosis, 7 had extra-cardiac thoracic sarcoidosis, and 11 had both cardiac and extra-cardiac thoracic sarcoidosis. On visual analysis for diagnosis of cardiac sarcoidosis, 4/20 ¹⁸F-FDG scans were rated as inconclusive because the ¹⁸F-FDG pattern was diffuse, whereas no FLT scans were rated as inconclusive. The sensitivity of ¹⁸F-FDG PET/CT for detection of cardiac sarcoidosis was 85%; specificity, 100%; and accuracy, 90%. The corresponding values for ¹⁸F-FLT PET/CT were 92, 100, and 95%, respectively. Using semiquantitative analysis of cardiac sarcoidosis, the mean ¹⁸F-FDG SUVmax was significantly higher than the mean ¹⁸F-FLT SUVmax (P < 0.005). Both ¹⁸F-FDG and ¹⁸F-FLT PET/CT studies detected all 24 extra-cardiac lesions. Using semiquantitative analysis of extra-cardiac sarcoidosis, the mean ¹⁸F-FDG SUVmax was significantly higher than the mean ¹⁸F-FLT SUVmax (P < 0.001).

Conclusions: The results of this preliminary study suggest that ¹⁸F-FLT PET/CT can detect cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis as well as ¹⁸F-FDG PET/CT, although uptake of ¹⁸F-FLT in lesions was significantly lower than that of ¹⁸F-FDG. However, ¹⁸F-FLT PET/CT may be easier to perform since it requires neither prolonged fasting nor a special diet prior to imaging.

Keywords: 18F-FDG; 18F-FLT; PET; Sarcoidosis.