Assessment of the Utility of the Radiotracer "FET"in PET Imaging of Recurrent Glioblastoma Multiforme (GBM): Monitoring Early Response to Antiangiogenic Therapy
The PET radiotracer FET provides a measure of large, neutral amino acid transport. This
transport is significantly upregulated in malignant brain tumors. FET rarely gives false
positive findings in the setting of inflammation seen after high dose chemotherapy or
radiotherapy. FET labels low-grade as well as high-grade gliomas, in contrast to FDG, which
almost exclusively labels only high-grade gliomas. FET imaging may prove to be particularly
useful in the setting of infiltrative tumor, which is not contrast-enhancing on MRI and
therefore not detectable with FDG. Management of glioblastoma patients with stable
contrast-enhancing disease on MRI but increased signs of edema is difficult. This is because
it is difficult to distinguish simple edema from infiltrative tumor. The former is managed
with steroids and the latter is managed with chemotherapy, and anti-angiogenic drugs.
FET may be particularly useful in assessing changes after GBM patients receive anti-vascular
agents such as Avastin. Avastin is very commonly used in patients after failure of
first-line treatment in GBM. Not only is Avastin costly, but it also can have serious side
effects such as internal bleeding and gastric perforation, severe hypertension, poor wound
healing, and renal toxicity. It is important to know when a patient is failing Avastin
treatment so that the drug can be discontinued. Preliminary data in Europe (see figures
below) suggests that FET-PET can accurately distinguish Avastin responders from
1. GBM patients with changes on MRI suggestive of recurrence who have not yet initiated
2. Age ≥ 18
3. Anticipated survival >3 months
4. Able to give informed consent
5. Capable of undergoing scan without the need for sedation or general anesthesia.
1. Active intracranial infection or nonglial brain mass.
2. Recent large intracranial hemorrhage (<1 month; size to be determined by principal
3. Pregnant or nursing. Quantitative serum hCG testing will be performed prior to the
initial and each -subsequent FET- PET scan on all females of childbearing potential.
Our BWH Radiation Safety Committee and Partners IRB requires stat serum ß-hcG pregnancy
4. Patient lives too far from BWH and/or is unwilling/ unable to return for scheduled
Endpoint Classification: Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Diagnostic
Change in FET uptake between baseline and follow-upm, relative to survival and progression on MRI
We will look for indicators of radiographic response on FET-PET using changes in SUV. These outcomes will be correlated with progression-free survival and overall survival.
Laura L Horky, MD, PhD
Brigham and Women's Hospital
United States: Food and Drug Administration
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