The feasibility of 11C-methionine-PET in diagnosis of solitary lung nodules/masses when compared with 18F-FDG-PET.
OBJECTIVE
To differentiate between benign and malignant lesions of the lung, 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) has limitations such as a lower specificity in cases of non-specific inflammation. The positive predictive value is unsatisfactory in countries where inflammatory lung disorders are prevalent. We present the preliminary results of the usefulness of combining 11C-methionine-PET and 18F-FDG-PET in this context.


METHODS
Fifteen patients with indeterminate solitary pulmonary nodules/masses (10 men, 5 women; average age 64.7 +/- 14.0 years, ranging from 25 to 87 years) were studied using 11C-methionine- and 18F-FDG-PET. Interpretations were primarily made on visual analysis with five-point scale and a consensus of two nuclear medicine physicians, using standardized uptake value as an accessory reference. Foci of abnormal radiotracer uptake were subsequently correlated with clinical follow-up, imaging modalities such as chest radiography, chest computed tomography (CT), serial PET studies, and pathology results from bronchoscopic biopsy and/or surgical specimen.


RESULTS
Diagnoses were established in 14 patients. The 11C-methionine-PET and 18F-FDG-PET studies were both true positive in two cases of adenocarcinoma and true negative in two cases of clinical benign nodules. In one case of lymphoid hyperplasia both 11C-methionine-PET and 18F-FDG-PET showed false-positive findings. Discordant results were obtained in nine cases. In spite of the false-positive results of 18F-FDG-PET, 11C-methionine-PET was true negative in four cases with chronic inflammatory nodules and three cases of pulmonary tuberculosis. Furthermore, (11)C-methionine-PET was true positive in one case of lung metastasis of thyroid cancer, and in another with recurrence of gastric cancer, respectively, for which 18F-FDG-PET imaging was false negative.


CONCLUSIONS
Our experience indicates that 11C-methionine-PET seems more specific and sensitive when compared with 18F-FDG-PET for the purpose of differentiating benign and malignant thoracic nodules/masses. The possibility of an FDG-avid lesion being malignant is decreased if it shows a negative result by 11C-methionine-PET.
Hsieh
Hung-Jen
HJ
Department of Nuclear Medicine, Buddhist Tzu Chi General Hospital, Hualien, Taiwan, China. hsiehhj@tzuchi.com.tw
Lin
Sheng-Hsiang
SH
Lin
Ko-Han
KH
Lee
Chien-Ying
CY
Chang
Cheng-Pei
CP
Wang
Shyh-Jen
SJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005240:Feasibility Studies; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis; D008297:Male; D008715:Methionine / Q000187:drug effects*; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000175:diagnosis*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C086242:carbon-11 methionine; D008715:Methionine