PET for glioblastoma
PET is more and more frequently used to visualize brain cancers. However, PET is not medically appropriate to follow glioblastoma because it not supported by credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community. PET for brain cancer is not included in the NCCN guidelines and CMS does not cover PET for this diagnosis. Occasionally, PET can provide information to differentiate tumor necrosis from tumor progression. Tumor necrosis is when a cancer dies after being treated. 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 grade, and small tumor volume. 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 PET after radiation and chemotherapy and the accuracy of PET in tumors other than high-grade gliomas.
A 2010 guideline by Laperrier says: “Positron emission tomography (PET) is not recommended for the determination of diagnosis or grading in gliomas. A recommendation cannot be made for or against the use of PET or positron emission tomography/computed tomography (PET/CT) in the assessment of patients with recurrent gliomas because of insufficient evidence. Positron emission tomography (PET) is not recommended for the determination of diagnosis or grading in gliomas. A recommendation cannot be made for or against the use of PET for the assessment of treatment response in gliomas because of insufficient evidence. A recommendation cannot be made for or against the use of PET or positron emission tomography/computed tomography (PET/CT) in the assessment of patients with recurrent gliomas because of insufficient evidence. Positron emission tomography (PET) is not recommended for the determination of diagnosis or grading in gliomas. A recommendation cannot be made for or against the use of PET for the assessment of treatment response in gliomas because of insufficient evidence. A recommendation cannot be made for or against the use of PET or positron emission tomography/computed tomography (PET/CT) in the assessment of patients with recurrent gliomas because of insufficient evidence.”
It is not clinically appropriate in terms of type, frequency, extent, site and duration and considered effective for the condition in question as per literature and guidelines
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