For PET brain cancers are not inlcuded in guidelines and CMS does not cover PET for this diangosis. Occasionally, PET can provide information to differntiate tumor necrosis from tumor progression. The sensitivity of PET for differentiating necrosis and tumor progression is 80%–90% and the specificity is 50%–90%. Causes of false-negative PET results include recent radiation therapy, low histologic grade, and small tumor volume. FDG PET may be false positive in nonmalignant inflammatory processes and subclinical seizure activity. The question of hypermetabolic foci of radiation injury as a cause of false-positive scans requires further investigation. Other issues requiring further study are the optimal timing of FDG PET after radiation and chemotherapy and the accuracy of FDG PET in tumors other than high-grade gliomas.
Is Current Imaging Good Enough to Differentiate Radiation-Induced Brain Injury from Tumor Recurrence?
AJNR Am. J. Neuroradiol., June 1, 2005; 26(6): 1305 – 1305.
Daniel D. Langleben and George M. Segall PET in Differentiation of Recurrent Brain Tumor from Radiation Injury The Journal of Nuclear Medicine Vol. 41 No. 11 1861-1867