Value of PET in the assessment of patients with neurofibromatosis type 1.
OBJECTIVE
The objective of our study was to investigate the use of PET in the detection of malignant peripheral nerve sheath tumors (MPNSTs) in patients with neurofibromatosis type 1 (NF1).


METHODS
Forty-five patients with NF1 who underwent whole-body PET for suspected MPNST based on clinical symptoms or radiologic examinations were retrospectively evaluated. Ten patients underwent additional carbon-11 (11C) methionine PET because of equivocal 18F-FDG PET findings or because of a discrepancy between the FDG PET and clinical findings. PET images were evaluated for the distribution and uptake pattern, and the standardized uptake values (SUVs) were obtained. Twenty-seven patients underwent biopsy or surgery of the detected lesions and 18 patients were followed up clinically and with repeat imaging studies.


RESULTS
Fifty lesions were identified on FDG PET. There were eight false-positive results and one false-negative on FDG PET. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FDG PET in detecting MPNSTs in patients with NF1 were 95%, 72%, 71%, 95%, and 82%, respectively. Using 11C methionine PET in combination with FDG PET reduced the number of false-positive results from eight to two, which increased the specificity from 72% to 91%. In five patients, 11C methionine FDG PET contributed additional information about nontarget lesions that influenced treatment planning.


CONCLUSIONS
FDG PET is a sensitive technique in the detection of MPNSTs in patients with NF1. The addition of 11C methionine PET increases specificity in equivocal cases. PET may improve preoperative tumor staging by detecting metastases or second primary tumors, which often are present in patients with NF1.
Bredella
Miriam A
MA
Department of Radiology, Massachusetts General Hospital, 55 Fruit St., Yawkey 6E, Boston, MA 02114, USA. mbredella@partners.org
Torriani
Martin
M
Hornicek
Francis
F
Ouellette
Hugue A
HA
Plamer
William E
WE
Williams
Ziv
Z
Fischman
Allan J
AJ
Plotkin
Scott R
SR
D000293:Adolescent; D000328:Adult; D000368:Aged; D002247:Carbon Isotopes; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008715:Methionine / Q000172:deficiency*; D008875:Middle Aged; D009456:Neurofibromatosis 1 / Q000000981:diagnostic imaging*; D010524:Peripheral Nervous System Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D051598:Whole Body Imaging / Q000379:methods
D002247:Carbon Isotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D008715:Methionine