PET in differentiation of recurrent brain tumor from radiation injury

The annual incidence of primary intracranial tumors is 7 to 19 cases per 100,000 people. The general approach to the treatment of brain neoplasms is surgical resection of solitary lesions or limited disease, followed by radiation therapy with or without chemotherapy. Multiple metastatic lesions are usually treated with whole-brain radiation. Radiation injury occurs in 5% to 37% of cases and can be difficult to differentiate from residual or recurrent malignancy by MRI. PET has been used to differentiate radiation injury from malignancy on the basis of differences in glucose uptake. Recent studies have reported the sensitivity and specificity of PET to be 81% to 86% and 40% to 94%, respectively. This article reviews the classification of primary brain tumors, the histologic changes associated with radiation injury, and the diagnostic and prognostic information provided by PET.