CNS 18 - 12 
4.2 Exclusion Criteria 
1. Acutely increased intracranial pressure (ICP) requiring prompt surgical 
(shunt, tumor resection) reduction. 
2. Tumors in direct contact with the ventricular or cisternal spaces (brain 
stem tumors, spinal cord tumors, superficially located cerebellar tumors). 
5.0 STUDY DESIGN AND TREATMENT 
This is a nonrandomized, Phase I toxicity study. Therapeutic intent is implied, and 
responses to treatment will be accessed. 
Patients who exhibit a partial response to therapy and no significant, irreversible toxicity, 
will be considered for repeated treatments based on their clinical status. 
5.1 Stereotactic Delivery' of Producer-Vector Cells 
Multiple CR or MRI-guided stereotactic injections of the HS-tk vector-producer 
cells into the brain tumor tissue will be done under general anesthesia. The 
number of injection points will be preplanned and determined by the size of the 
tumor. Each injection will be done using a volumetric pump over 10-30 minutes 
duration. 
5.1.1 Volume and Number of Injected Cells 
The tumor size, shape, and location will determine the number and 
spacing of stereotactic injections. The cannula placement will be targeted 
at roughly 3 mm spacing homogeneously within the tumor volume. The 
producer-vector cell concentration is 1 x 10 s cells/ml; between 1 x 10 5 and 
2 x 10 9 cells will be administered within the tumor. 
5.1.2. Disposal of residual producer cells. 
Residual cells and the accompanying vial will be placed in an infectious 
w'aste container and autoclaved before disposal. 
5.2 Peri- Operative Medications 
5.2. 1 ATUibiorics : All patients will receive a single dose of Ceftriaxone (2 g nr 
IV) just prior to the surgical procedure. 
5.2.2 Steroids : Dexamethasone (16 mg/m 2 /day in 3 divided doses) will be 
started 3 days prior to the stereotactic injection of vector-producer cells 
and continued until GCV is discontinued. Dexamethasone will then be 
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