The neuropharmacokinetics of temozolomide in patients with resectable brain tumors: potential implications for the current approach to chemoradiation.
OBJECTIVE
Intracerebral microdialysis (ICMD) is an accepted method for monitoring changes in neurochemistry from acute brain injury. The goal of this pilot study was to determine the feasibility of using ICMD to examine the neuropharmacokinetics of temozolomide in brain interstitium following oral administration.


METHODS
Patients with primary or metastatic brain tumors had a microdialysis catheter placed in peritumoral brain tissue at the time of surgical debulking. Computerized tomography scan confirmed the catheter location. Patients received a single oral dose of temozolomide (150 mg/m2) on the first postoperative day, serial plasma and ICMD samples were collected over 24 hours, and temozolomide concentrations were determined by tandem mass spectrometry.


RESULTS
Nine patients were enrolled. Dialysate and plasma samples were successfully collected from seven of the nine patients. The mean temozolomide areas under the concentration-time curve (AUC) in plasma and brain interstitium were 17.1 and 2.7 microg/mL x hour, with an average brain interstitium/plasma AUC ratio of 17.8%. The mean peak temozolomide concentration in the brain was 0.6 +/- 0.3 microg/mL, and the mean time to reach peak level in brain was 2.0 +/- 0.8 hours.


CONCLUSIONS
The use of ICMD to measure the neuropharmacokinetics of systemically administered chemotherapy is safe and feasible. Concentrations of temozolomide in brain interstitium obtained by ICMD are consistent with published data obtained in a preclinical ICMD model, as well as from clinical studies of cerebrospinal fluid. However, the delayed time required to achieve maximum temozolomide concentrations in brain suggests that current chemoradiation regimens may be improved by administering temozolomide 2 to 3 hours before radiation.
Department of Medical Oncology and Experimental Therapeutics, 1500 East Duarte Road, Duarte, CA 91010, USA. jportnow@coh.org
Jana
J
Portnow
Behnam
B
Badie
Mike
M
Chen
An
A
Liu
Suzette
S
Blanchard
Timothy W
TW
Synold
D000284:Administration, Oral; D000368:Aged; D018906:Antineoplastic Agents, Alkylating / Q000493:pharmacokinetics; D019540:Area Under Curve; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy* / Q000601:surgery; D003131:Combined Modality Therapy / Q000379:methods; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D017551:Microdialysis; D008875:Middle Aged; D010865:Pilot Projects; D011878:Radiotherapy / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods; D000077204:Temozolomide
D018906:Antineoplastic Agents, Alkylating; D003606:Dacarbazine; D000077204:Temozolomide