Salvage intracerebrospinal fluid thiotepa in breast cancer-related leptomeningeal metastases: a retrospective case series.

There is currently a paucity of data on salvage intracerebrospinal fluid (intra-CSF) chemotherapy in leptomeningeal metastases (LM). This report is a single-institution experience with salvage treatment in patients with breast cancer (BC) and LM. This retrospective cohort describes 24 consecutive patients with BC selected for a second-line of treatment for LM. The first line of LM treatment consisted of intra-CSF liposomal cytarabine in all patients combined with systemic therapy in 18 cases and radiotherapy in four cases. Second-line (salvage) treatment utilized intra-CSF thiotepa in all and systemic chemotherapy in nine patients. No patient received CNS-directed radiotherapy. The median Eastern Cooperative Oncology Group performance status at initiation of intra-CSF thiotepa treatment was 3 (range 1-4). The median progression-free survival and median survival following intra-CSF thiotepa was 3.1 months (range 3 days-2 years) and 4.0 months (range 6 days-2.5 years), respectively. The median overall survival from LM diagnosis was 9.5 months (range 1.3 months-2.7 years). No grade 3 or higher toxicity was observed. Recognizing the limits of a retrospective study, intra-CSF thiotepa has an acceptable toxicity profile and appears to be a reasonable option for selected BC patients.

Penetration of ifosfamide and its active metabolite 4-OH-ifosfamide into cerebrospinal fluid of patients with CNS malignancies.

PURPOSE: The aim of this study was to examine the penetration of ifosfamide (IFO) and 4-hydroxy-ifosfamide (4-OH-IFO) into the CSF of human adults and to evaluate the influence of blood-CSF barrier (BCB) function. METHODS: In 12 adult patients with a malignant CNS disease treated with IFO 1,300-2,000 mg/m(2)/d as a 3-hour intravenous infusion, 17 CSF samples were collected within 10 min after the end of IFO infusion. In 8 of these patients, the CSF was obtained in up to 5 sequential 2-ml portions to detect a potential caudocranial concentration gradient. Additionally, blood was collected before treatment and immediately following IFO infusion. RESULTS: IFO was detected in all 17 CSF samples at a median concentration of 79.24 µmol/l (39.27-176.73) and a median CSF/plasma ratio of 0.38 (0.18-0.72). 4-OH-IFO was detected in 11 CSF samples from 7 patients at a median concentration of 4.1 µmol/l (2.44-36.03) and a median CSF/plasma ratio of 3.07 (0.62-29.12). 4-OH-IFO was undetectable in 6 CSF samples from 5 patients and in one plasma sample. Both CSF drug concentrations and their CSF/plasma quotients neither correlated with steroid comedication nor with albumin quotients (QAlb). CONCLUSIONS: Both IFO and 4-OH-IFO can penetrate into the CSF of human adults without a correlation to CSF turnover. In contrast to IFO, 4-OH-IFO CSF penetration is not reliable with levels ranging between undetectable and exceeding those in the corresponding plasma.

Predicting human tumor drug concentrations from a preclinical pharmacokinetic model of temozolomide brain disposition.

PURPOSE: Knowledge of drug concentrations in tumors is critical for understanding the determinants of drug accumulation in tumors. Because significant obstacles prevent making these measurements in humans, development of a predictive pharmacokinetic model would be of great value to the translation of preclinical data to the clinic. Our goal was to show how the latter could be achieved for temozolomide, an agent used in the treatment of brain tumors, using an orthotopic brain tumor model in rats. EXPERIMENTAL DESIGN: Rats bearing i.c. tumors received 20 mg/kg i.v. of temozolomide followed by the subsequent measurement of serial plasma, cerebrospinal fluid (CSF), normal brain, and brain tumor temozolomide concentrations. The resultant data provided the framework to develop a hybrid physiologically based pharmacokinetic model for temozolomide in brain. The preclinical pharmacokinetic model was scaled to predict temozolomide concentrations in human CSF, normal brain, and brain tumor, and through a series of Monte Carlo simulations, the accumulation of temozolomide in brain tumors under conditions of altered blood-brain barrier permeability, fractional blood volume, and clinical dosing schedules was evaluated. RESULTS: The developed physiologically based pharmacokinetic model afforded a mechanistic and accurate prediction of temozolomide brain disposition in rats, which through model scale-up procedures accurately predicted the CSF/plasma area under the drug concentration-time curve ratios of 0.2 reported in patients. Through a series of model simulations, it was shown that the brain tumor accumulation of temozolomide varied substantially based on changes in blood-brain barrier permeability and fractional tumor blood volume but minimally based on clinical dosing regimens. CONCLUSIONS: A physiologically based pharmacokinetic modeling approach offers a means to translate preclinical to clinical characteristics of drug disposition in target tissues and, thus, a means to select appropriate drug dosing regimens for achieving optimal target tissue drug concentrations.

Management of leptomeningeal malignancy.

Leptomeningeal carcinomatosis is defined as malignant infiltration of the pia matter and arachnoid membrane. Leukaemias and lymphomas, lung, breast cancer and melanoma are the primary tumours commonly associated with leptomeningeal carcinomatosis. Diagnosis is based on compatible symptoms and signs, cytological evidence of malignancy in the cerebrospinal fluid, and neuroimaging studies. Treatment is largely palliative (median survival 2-4 months). Patients with lympomatous or leukaemic meningitis, chemosensitive tumours such as breast cancer, low tumour burden, minimal neurological deficits, good performance status and controllable systemic disease survive longer with occasional long-term responses. Available treatment options include focal radiation therapy to CNS sites of bulky, symptomatic or obstructive meningeal deposits, intrathecal cytotoxic therapy and systemic chemotherapy. No evidence of superiority of intrathecal treatment compared with best palliative care (including radiation therapy and systemic treatment) is available from clinical trials. Novel treatment approaches include intrathecal liposomal Ara-C, the development of new cytotoxic compounds, signal transduction inhibitors and monoclonal antibodies for intrathecal or systemic use. Until data from multi-centre randomised trials are available, rationalisation of therapy should be done by stratifying patients to prognostic groups. High-risk patients will only survive for a few weeks and are better managed with supportive measures, whereas low-risk patients justify vigorous cerebrospinal fluid-directed treatment combined with radiation therapy and systemic chemotherapy.

Plasma and cerebrospinal fluid population pharmacokinetics of temozolomide in malignant glioma patients.

PURPOSE: Scarce information is available on the brain penetration of temozolomide (TMZ), although this novel methylating agent is mainly used for the treatment of malignant brain tumors. The purpose was to assess TMZ pharmacokinetics in plasma and cerebrospinal fluid (CSF) along with its inter-individual variability, to characterize covariates and to explore relationships between systemic or cerebral drug exposure and clinical outcomes. EXPERIMENTAL DESIGN: TMZ levels were measured by high-performance liquid chromatography in plasma and CSF samples from 35 patients with newly diagnosed or recurrent malignant gliomas. The population pharmacokinetic analysis was performed with nonlinear mixed-effect modeling software. Drug exposure, defined by the area under the concentration-time curve (AUC) in plasma and CSF, was estimated for each patient and correlated with toxicity, survival, and progression-free survival. RESULTS: A three-compartment model with first-order absorption and transfer rates between plasma and CSF described the data appropriately. Oral clearance was 10 liter/h; volume of distribution (V(D)), 30.3 liters; absorption constant rate, 5.8 h(-1); elimination half-time, 2.1 h; transfer rate from plasma to CSF (K(plasma-->CSF)), 7.2 x 10(-4)h(-1) and the backwards rate, 0.76 h(-1). Body surface area significantly influenced both clearance and V(D), and clearance was sex dependent. The AUC(CSF) corresponded to 20% of the AUC(plasma). A trend toward an increased K(plasma-->CSF) of 15% was observed in case of concomitant radiochemotherapy. No significant correlations between AUC in plasma or CSF and toxicity, survival, or progression-free survival were apparent after deduction of dose-effect. CONCLUSIONS: This is the first human pharmacokinetic study on TMZ to quantify CSF penetration. The AUC(CSF)/AUC(plasma) ratio was 20%. Systemic or cerebral exposures are not better predictors than the cumulative dose alone for both efficacy and safety.

Plasma and cerebrospinal fluid pharmacokinetics of intravenous temozolomide in non-human primates.

Temozolomide is a prodrug that undergoes spontaneous chemical degradation at physiologic pH to form the highly reactive alkylating agent, methyl-triazenyl imidazole carboxamide (MTIC). In clinical trials, temozolomide has activity in gliomas and is approved for recurrent anaplastic astrocytoma. We, therefore, studied the penetration of temozolomide into the cerebrospinal fluid (CSF) as a surrogate for blood-brain barrier penetration in a non-human primate model. Three Rhesus monkeys with indwelling Ommaya reservoirs received 7.5 mg/kg (150 mg/m2) of temozolomide as a 1 h intravenous infusion. Frequent blood and CSF samples were obtained over 24 h, plasma was immediately separated by centrifugation at 4 degrees C, and plasma and CSF samples were acidified with HCl. Temozolomide concentration in plasma and CSF was measured by reverse-phase high-pressure liquid chromatography. Plasma temozolomide concentration peaked 0.5 h after the end of the infusion and was 104 +/- 3 microM. The mean peak CSF temozolomide concentration was 26 +/- 4 microM at 2.5 h. The mean areas under the temozolomide concentration-time curves in plasma and CSF were 392 +/- 18 and 126 +/- 18 microM h, respectively, and the CSF: plasma ratio was 0.33 +/- 0.06. Clearance of temozolomide was 0.116 +/- 0.004 l/kg/h, and the volume of distribution at steady state was 0.254 +/- 0.033 l/kg. In this non-human primate model, temozolomide penetrated readily across the blood-brain barrier. These findings are consistent with the activity of temozolomide in brain tumors.

Improved efficacy of chemotherapy for glioblastoma by radiation-induced opening of blood-brain barrier: clinical results.

PURPOSE: To improve the efficacy of chemotherapy for glioblastoma through the radiation-induced opening of the blood-brain barrier (BBB). METHODS AND MATERIALS: In two previous articles, we have described the results of brain scanning using technetium 99m-labeled somatostatin and the measurement of methotrexate (MTX) concentrations in blood and cerebrospinal fluid (CSF) after i.v. injection. We discovered that the BBB and blood-cerebrospinal fluid barrier opened to a certain extent after 20- to 40-Gy irradiation, thus increasing the degree to which MTX permeated the brain tissue. On the basis of these findings, we retrospectively analyzed the outcome in 56 patients with glioblastoma given either chemotherapy (CCNU) after 20- to 40-Gy irradiation (28 patients) or radiation therapy alone (28 patients). RESULTS: The 1-, 3-, and 5-year survival rates were 57.14%, 22.50%, and 15.00% in the combined-therapy group and 17.86%, 7.14%, and 3.57% in the radiotherapy alone group, respectively. The respective median survival times were 29.11 +/- 6.99 and 9.86 +/- 3.45 months (p < 0.001), which represented a statistically significant difference. CONCLUSION: Our study further confirms that opening of the BBB induced by irradiation with 20-40 Gy may optimize the effects of intracranial chemotherapy.

Pharmacokinetics of ifosfamide and some metabolites in children.

The pharmacokinetics of ifosfamide and some metabolites in children was investigated. The patients received various doses of ifosfamide, mostly by continuous infusion, over several days. The penetration of ifosfamide and its metabolites into the cerebrospinal fluid was also studied in four cases. Ifosfamide and 4-hydroxyifosfamide pass the blood-brain barrier, reaching cerebrospinal fluid concentrations that are almost as high as plasma concentrations.