Continuous intratumoral infusion of methotrexate for recurrent glioblastoma: a pilot study

Convection-enhanced delivery for the treatment of glioblastoma

Effective treatment of glioblastoma (GBM) remains a formidable challenge. Survival rates remain poor despite decades of clinical trials of conventional and novel, biologically targeted therapeutics. There is considerable evidence that most of these therapeutics do not reach their targets in the brain when administered via conventional routes (intravenous or oral). Hence, direct delivery of therapeutics to the brain and to brain tumors is an active area of investigation. One of these techniques, convection-enhanced delivery (CED), involves the implantation of catheters through which conventional and novel therapeutic formulations can be delivered using continuous, low-positive-pressure bulk flow. Investigation in preclinical and clinical settings has demonstrated that CED can produce effective delivery of therapeutics to substantial volumes of brain and brain tumor. However, limitations in catheter technology and imaging of delivery have prevented this technique from being reliable and reproducible, and the only completed phase III study in GBM did not show a survival benefit for patients treated with an investigational therapeutic delivered via CED. Further development of CED is ongoing, with novel catheter designs and imaging approaches that may allow CED to become a more effective therapeutic delivery technique.

The "Trojan Horse" approach to tumor immunotherapy: targeting the tumor microenvironment

Most anticancer therapies including immunotherapies are given systemically; yet therapies given directly into tumors may be more effective, particularly those that overcome natural suppressive factors in the tumor microenvironment. The “Trojan Horse” approach of intratumoural delivery aims to promote immune-mediated destruction by inducing microenvironmental changes within the tumour at the same time as avoiding the systemic toxicity that is often associated with more “full frontal” treatments such as transfer of large numbers of laboratory-expanded tumor-specific cytotoxic T lymphocytes or large intravenous doses of cytokine. Numerous studies have demonstrated that intratumoural therapy has the capacity to minimizing local suppression, inducing sufficient “dangerous” tumor cell death to cross-prime strong immune responses, and rending tumor blood vessels amenable to immune cell traffic to induce effector cell changes in secondary lymphoid organs. However, the key to its success is the design of a sound rational approach based on evidence. There is compelling preclinical data for local immunotherapy approaches in tumor immunology. This review summarises how immune events within a tumour can be modified by local approaches, how this can affect systemic antitumor immunity such that distal sites are attacked, and what approaches have been proven most successful so far in animals and patients.

The effect of ABCG2 and ABCC4 on the pharmacokinetics of methotrexate in the brain

Methotrexate (MTX) is the cornerstone of chemotherapy for primary central nervous system lymphoma, yet how the blood-brain barrier (BBB) efflux transporters ABCG2 and ABCC4 influence the required high-dose therapy is unknown. To evaluate their role, we used four mouse strains, C57BL/6 (wild-type; WT), Abcg2(-/-), Abcc4(-/-), and Abcg2(-/-);Abcc4(-/-) (double knockout; DKO) to conduct brain microdialysis studies after single intravenous MTX doses of 50 mg/kg. When the area under the concentration-time curve for plasma (AUC(plasma)) was used to assess systemic exposure to MTX, the rank order was Abcc4(-/-) < WT < Abcg2(-/-) < Abcg2(-/-)Abcc4(-/-). Only the DKO exposure was significantly higher than that of the WT group (P < 0.01), a reflection of the role of Abcg2 in biliary excretion and Abcc4 in renal excretion. MTX brain interstitial fluid concentrations obtained by microdialysis were used to calculate the area under the concentration-time curve for the brain (AUC(brain)), which found the rank order of exposure to be WT < Abcc4(-/-) < Abcg2(-/-) < Abcg2(-/-)Abcc4(-/-) with the largest difference being 4-fold: 286.13 ± 130 μg*min/ml (DKO) versus 66.85 ± 26 (WT). Because the transporters affected the systemic disposition of MTX, particularly in the DKO group, the ratio of the AUC(brain)/AUC(plasma) or the brain/plasma partition coefficient Kp was calculated, revealing that the DKO strain had a significantly higher value (0.23 ± 0.09) than the WT strain (0.11 ± 0.05). Both Abcg2 and Abcc4 limited BBB penetration of MTX; however, only when both drug efflux pumps were negated did the brain accumulation of MTX significantly increase. These findings indicate a contributory role of both ABCG2 and ABCC4 to limiting MTX distribution in patients.

Intratumoral doxorubicin in patients with malignant brain gliomas

The objective of the study was to evaluate the safety and therapeutic efficacy of intralesional administration of doxorubicin in brain gliomas. Ten patients with recurrent grade III or IV glioma were enrolled in the study, after the second operation. All patients had not responded to radiation therapy. Chemotherapy was administered directly in the tumor through an Ommaya pump placed in the site of disease at the time of craniotomy. Doxorubicin 0.5 mg was administered in the Ommaya reservoir every 24 hours on days 1 to 10. Patients were evaluated at 6- to 8-week intervals until tumor progression and death. All patients were evaluated for response. Six of 10 patients had clinical improvement lasting from 12 to 73 weeks. Objective radiologic response was observed in 5 of 10 (50%) patients. One patient achieved complete response with time to disease progression of 119 weeks, and 4 patients had a partial response (duration 14-39 weeks) with 25% or more reduction of tumor volume on computed tomography scan compared with pretreatment measurements. Time to disease progression in patients who responded after the intratumoral chemotherapy was 39.83 +/- 40.5 weeks. One additional patient had stable disease for a duration of 12 weeks. The median survival of the patients with response was 55.17 +/- 54.22 weeks (range: 21-164 weeks), whereas survival of those who did not respond was 17.0 +/- 12.36 weeks (range: 8-35) (Mann Whitney U test: z = -2.13, p = 0.033). The median survival of all 10 patients was 39.9 +/- 45.52 weeks (range: 8-73 weeks). Bifrontal headache was reported in 4 of 10 patients immediately after the administration of doxorubicin. There were no other clinically significant adverse reactions either in the brain or systematically. Intralesional administration of doxorubicin appears to be a safe and effective treatment and should be further explored in the management of brain gliomas resistant to conventional forms of treatment.

Pharmacokinetics of methotrexate in the extracellular fluid of brain C6-glioma after intravenous infusion in rats

PURPOSE

Establishment of the pharmacokinetic profile of methotrexate (MTX) in the extracellular fluid (ECF) of a brain C6-glioma in rats.

METHODS

Serial collection of plasma samples and ECF dialysates after i.v. infusion of MTX (50 or 100 mg/kg) for 4 h. HPLC assay.

RESULTS

Histological studies revealed the presence of inflammation, edema, necrosis, and hemorrhage in most animals. In vivo recovery (reverse dialysis) was 10.8 +/- 5.3%. MTX concentrations in tumor ECF represented about 1-2% of the plasma concentrations. Rapid equilibration between MTX levels in brain tumor ECF and plasma. ECF concentrations almost reached steady-state by the end of the infusion (4 h), then decayed in parallel with those in plasma. Doubling of the dose did not modify MTX pharmacokinetic parameters (t1/2alpha, t1/2beta, MRT, fb, Vd, and CL(T)), except for a 1.7-fold increase of AUC(Plasma) and a 3.8-fold increase in AUC(ECF), which resulted in a 2.3-fold increase in penetration (AUC(ECF)/AUC(Plasma)). In spite of an important interindividual variability, a relationship between MTX concentrations in plasma and tumor ECF could be established from mean pharmacokinetic parameters.

CONCLUSIONS

High plasma concentrations promote the penetration of MTX into brain tissue. However, free MTX concentrations in tumor ECF remain difficult to predict consistently.

Current perspectives in gliomas

The annual incidence of primary central nervous system tumors, including gliomas, is increasing, however, the prognosis of these tumors remains poor with a median survival of only 5 years. The imaging of tumors by computerised tomography, magnetic resonance imaging and newer methods such as positron emission tomography and proton magnetic resonance spectroscopy (1H-MRS) is increasing our knowledge of tumor biology and extent of the disease. Advances within the field of neurosurgery have improved operative procedures reducing mortality and morbidity. Furthermore, radiotherapy planning, tumor targeting and repositioning for treatment have all improved initial tumor management. The role of adjuvant chemotherapy remains controversial. Chemotherapy for advanced and recurrent disease has been extensively investigated, and although improvements in quality of life have been recorded, no prolongation of survival has been documented. With new discoveries and increasing knowledge of the physiology and molecular biology of these tumors the potential for targeting therapy at a genetic level is becoming increasingly promising. This review provides an overview of these current perspectives in glioma management.

Convection-enhanced delivery of macromolecules in the brain

For many compounds (neurotrophic factors, antibodies, growth factors, genetic vectors, enzymes) slow diffusion in the brain severely limits drug distribution and effect after direct drug administration into brain parenchyma. We investigated convection as a means to enhance the distribution of the large and small molecules 111In-labeled transferrin (111In-Tf; M(r), 80,000) and [14C]sucrose (M(r), 359) over centimeter distances by maintaining a pressure gradient during interstitial infusion into white matter to generate bulk flow through the brain interstitium. The volume of distribution (Vd) containing > or = 1% concentration of infusion solution increased linearly with the infusion volume (Vi) for 111In-Tf(Vd/Vi, 6:1) and [14C]sucrose (Vd/Vi, 13:1). Twenty-four hours after infusion, the distribution of 111In-Tf was increased and more homogeneous, and penetration into gray matter had occurred. By using convection to supplement simple diffusion, enhanced distribution of large and small molecules can be obtained in the brain while achieving drug concentrations orders of magnitude greater than systemic levels.