the vector can carry the tk gene into your brain tumor cells. When the vector/gene 
combination gets into your tumor cells it inserts itself into the cells' command center 
(nucleus) and tells the tumor cells to begin making thymidine kinase. When we give you 
Cytovene®, the tumor cells containing the tk gene produce harmful substances within 
themselves that cause the tumor cells to die. We do not expect normal brain cells to be 
injured because the converted Cytovene® is harmful only to rapidly growing cells. Normal 
cells in the brain are not rapidly growing but tumor cells are and therefore are targets for the 
vector/gene/Cytovene® combination. 
Pretreatment Evaluation: 
You have had most of these procedures before your first operation for your brain 
tumor. You will have a complete neurological and physical examination and blood and urine 
tests to determine your overall health. The amount of blood drawn from you will be no more 
than 18 teaspoons (3 ounces) in one day. You may experience some discomfort or 
temporary pain at the site of the needle entry for the routine blood studies. There is remote 
risk of fainting and local infection. 
You will also have radiographic examinations of your chest and head and any other 
areas of the body as indicated by your medical examination and history. An 
electrocardiogram will be performed. Additional tests may be required depending upon your 
state of health and prior therapies. The blood tests will also include a test for the HIV (AIDS) 
virus. You will be asked to read and sign another Informed Consent Form for this test. If the 
test indicates that you may have an HIV infection this information will be discussed with you 
and you will be given an appointment with the Department of Infectous Diseases for more 
information. Patients with HIV will not be eligible for this protocol since the experimental 
treatment could interfere with the treatment for an HIV infection. 
An MRI scan and/or a CT scan of your brain will be done. Both scans are designed to 
examine the changes in the nervous system that occur with the recurrence of the brain 
tumor. MRI uses a strong magnetic field and radio waves to show structural and chemical 
changes in the brain tissues. A CT scan uses x-rays. A single CT scan is equivalent to 
about 200 chest x-rays. The type of scan chosen will depend upon the status of your tumor 
and the response to this therapy. During the scan, a needle will be placed into a vein in your 
arm and an image enhancing contrast agent may be administered through that vein before 
obtaining a second set of scans. Each scan takes about 60 to 90 minutes. Scans will be 
repeated periodically after injection of the vector producing cells to monitor the effects of this 
therapy on tumor growth. 
Your will also be asked to take a series of simple memory and comprehension tests to 
establish a baseline before receiving the virus injection. Later, after the experimental 
treatment, you will be asked to take the tests again. This will help us determine the effect of 
the treatment. 
II. TREATMENT 
Surgery: 
The following procedure may be similar to procedures that you have already 
experienced when you were first treated for your brain tumor. A metal halo will be placed on 
your head to enable the doctors to precisely locate the tumor following a CT scan. This halo 
Recombinant DNA Research, Volume 20 
