Differentiating recurrent tumor from radiation necrosis: time for re-evaluation of positron emission tomography?
Our purpose was to evaluate the ability of FDG PET to differentiate recurrent tumor from posttherapy radiation necrosis.


METHODS
MR images, PET scans, and medical records of 84 consecutive patients with a history of a treated intracranial neoplasm were evaluated retrospectively. In all patients, recurrent tumor or radiation necrosis was suggested by clinical or MR findings. Metabolic activity of the PET abnormality was compared qualitatively with normal contralateral gray and white matter.


RESULTS
PET findings were confirmed histologically in 31 patients. With contralateral white matter as the standard of comparison, the PET scan sensitivity and specificity were found to be 86% and 22%, respectively. With contralateral gray matter as the reference standard, the sensitivity and specificity became 73% and 56%, respectively. Overall, nearly one third of the patients would have been treated inappropriately in either scheme had the PET scan been the sole determinant of therapy.


CONCLUSIONS
Our data suggest that the ability of FDG PET to differentiate recurrent tumor from radiation necrosis is limited. Both false-positive and false-negative PET scan results contributed to unacceptably low sensitivity and specificity values.
Ricci
P E
PE
Department of Neuroradiology, Barrow Neurological Institute, Phoenix, AZ 85001, USA.
Karis
J P
JP
Heiserman
J E
JE
Fram
E K
EK
Bice
A N
AN
Drayer
B P
BP
D003937:Diagnosis, Differential; D019788:Fluorodeoxyglucose F18; D006801:Humans; D009336:Necrosis; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging*; D011832:Radiation Injuries / Q000000981:diagnostic imaging*; D011859:Radiography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014055:Tomography, Emission-Computed
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18