Diagnostic usefulness of fluorine-18-alpha-methyltyrosine positron emission tomography in combination with 18F-fluorodeoxyglucose in sarcoidosis patients.
OBJECTIVE
L-[3-(18)F]-alpha-methyltyrosine ((18)F-FMT) is an amino-acid tracer for positron emission tomography (PET) and is used for tumor detection because malignant tumor cells accumulate (18)F-FMT based on the increased expression of an amino-acid transporter. This study was conducted to investigate the usefulness of (18)F-FMT PET in combination with fluorine-18-fluorodeoxyglucose ((18)F-FDG) PET for the diagnosis of sarcoidosis in patients with suspected malignancy.


METHODS
Twenty-four sarcoidosis patients with suspected malignancy underwent (18)F-FDG and (18)F-FMT PET. The study included 17 patients with extrapulmonary manifestation mimicking malignant disease (13 patients with systemic lymphadenopathy, 3 of them with concomitant hepatosplenic processes; 3 patients with hepatosplenic processes without concomitant lymphadenopathy; and 1 patient with multiple bone lesions), 3 patients with occurrence of bilateral hilar lymphadenopathy in cancer patients, and 4 patients with multiple nodules mimicking pulmonary metastasis.


RESULTS
All patients showed increased uptake of (18)F-FDG and no increase in the accumulation of (18)F-FMT in their lymphadenopathy. Standardized uptake values (SUVs) of (18)F-FDG and (18)F-FMT were 5.01 +/- 2.15 and 0.77 +/- 0.24, respectively (mean +/- SD). All extranodal lesions such as liver, spleen, and bone were visually positive on (18)F-FDG PET and negative on (18)F-FMT PET. No neoplasm was confirmed in all patients. In a control group of patients with lung cancer, SUVs for (18)F-FDG and (18)F-FMT were 6.34 +/- 2.52 and 1.54 +/- 0.82, respectively.


CONCLUSIONS
The uptake of (18)F-FDG was positive in the sarcoid lesions, and therefore (18)F-FDG PET could not differentiate sarcoidosis from malignant disease. Use of (18)F-FMT PET in combination with (18)F-FDG PET may be the effective method to distinguish sarcoidosis from malignancy.
Kaira
Kyoichi
K
Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma 371-8511, Japan. kkaira1970@yahoo.co.jp
Oriuchi
Noboru
N
Otani
Yoshimi
Y
Yanagitani
Noriko
N
Sunaga
Noriaki
N
Hisada
Takeshi
T
Ishizuka
Tamotsu
T
Endo
Keigo
K
Mori
Masatomo
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D001999:Bronchoscopy; D003937:Diagnosis, Differential; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis; D008297:Male; D008781:Methyltyrosines; D008875:Middle Aged; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012507:Sarcoidosis / Q000000981:diagnostic imaging*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
C105991:3-fluoro-alpha-methyltyrosine; D005462:Fluorine Radioisotopes; D008781:Methyltyrosines; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18