Evaluating Tumor Pseudoprogression With FLT-PET and MRI

A standard treatment for glioblastoma is a combination of radiation and the drug
temozolomide. This combination sometimes causing swelling (inflammation) of the brain
tissue. When standard monitoring with MRI or CT scans is done within a few months of
finishing treatment, it may be hard to tell if the scans are showing post-treatment brain
inflammation or tumor growth and worsening of disease. Currently the only way to
definitively distinguish inflammation from tumor growth is biopsy.

However, biopsy is an invasive procedure that is associated with risks. Having a
non-invasive method to distinguish post-treatment inflammation from tumor growth can help
improve care for patients with glioma.

For the PET scans in this research study, the investigators are using a radioactive
substance called FLT (3'-deoxy-3'-[F-18] fluorothymidine), instead of the standard substance
FDG (fluorodeoxyglucose). FLT gets absorbed by cancer cells but not by areas of
inflammation. Because of that FLT may be better than FDG in differentiating cancer cells
from inflammation.

An MRI scan will also be done at the same time as each of the 2 FLT-PET scans done for this
research study. The two MRI scans performed will also help give more information about the
patient's tumor that is not routinely provided with a routine clinical scan, such as blood
flow through the tumor or metabolic activity in the tumor. The information from these
special MRI scans may provide more information about the blood supply to the tumor and how
this changes in response to treatment. In addition, the MRI scans along with the FLT-PET
scans may help how to distinguish inflammation due to radiation therapy from tumor growth.